Herb Crusted Vegetable Gratin

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A gratin works because it does two things at once: steams the vegetables from below while crisping the top layer from above. The result is a dish with textural contrast in every bite.

This version uses a mix of potato, zucchini, and ripe tomato sliced thin so they cook evenly. The crust is breadcrumbs, Parmesan, garlic, rosemary, and thyme, pressed lightly over the top before baking.

It holds its shape well enough to serve in squares, which makes it practical for a weeknight side or a light lunch with a green salad. It also reheats without going soggy, so leftovers are worth keeping.

No cream, no bechamel. The natural juices from the tomato and zucchini do enough work to keep the vegetables moist underneath that crust.

Why You’ll Love This Recipe

• Crisp herb crust stays crunchy even after resting
• No cream or heavy sauce needed for rich flavor
• Holds well and reheats cleanly the next day
• Works as a side dish or a standalone light meal

Ingredient Notes

• Yukon Gold potatoes: Yukon Golds hold their shape better than russets when sliced thin and layered. Waxy varieties like red bliss also work well here.
• Zucchini: Medium zucchini works best. Large ones tend to hold too much water and can make the base soggy. Yellow summer squash is a direct swap.
• Ripe tomatoes: Use the ripest tomatoes you have, Roma or vine-ripened. They release just enough liquid to create a light sauce at the bottom of the dish.
• Panko breadcrumbs: Panko gives a lighter, crispier crust than regular breadcrumbs. Regular dried breadcrumbs work but pack tighter and brown faster, so watch the oven.
• Parmesan: Freshly grated Parmesan melts into the crust better than pre-grated. Pecorino Romano is a saltier substitute with a sharper edge.
• Fresh rosemary and thyme: Fresh herbs hold up better in the hot oven than dried in terms of aroma. If using dried, cut the quantity by half.

Herb Crusted Vegetable Gratin

A layered vegetable gratin with zucchini, potato, and tomato topped with a crisp rosemary-Parmesan breadcrumb crust, baked until golden.

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Prep Time 20 minutes mins

Cook Time 45 minutes mins

Total Time 1 hour hr 15 minutes mins

Servings: 4 servings

Calories: 295

Ingredients Method Notes

Ingredients

  

Vegetables

• 400 g Yukon Gold potatoes peeled and sliced 3 mm thin
• 350 g zucchini about 2 medium, sliced 3 mm thin
• 300 g ripe tomatoes about 3 medium Roma or vine-ripened, sliced 3 mm thin
• 1 medium yellow onion halved and thinly sliced
• 3 cloves garlic minced
• 3 tbsp olive oil divided
• 1 tsp fine sea salt divided
• 1/2 tsp black pepper freshly ground

Herb Crust

• 60 g panko breadcrumbs about 3/4 cup
• 50 g Parmesan freshly grated, about 1/2 cup
• 1 tbsp fresh rosemary finely chopped
• 1 tbsp fresh thyme leaves stripped from stems
• 1 clove garlic minced
• 2 tbsp olive oil
• 1/4 tsp fine sea salt

Method

 

Prep

1. Heat the oven to 200 C / 390 F. Brush a 9x13 inch baking dish generously with 1 tbsp olive oil.
2. Place zucchini slices in a single layer on a paper towel-lined tray. Sprinkle with 1/4 tsp salt, rest 10 minutes, then pat dry with paper towels.
3. Heat 1 tbsp olive oil in a small pan over medium heat. Add the sliced onion and a pinch of salt. Cook for 6 to 8 minutes, stirring occasionally, until soft and translucent but not browned. Add the minced garlic for the last minute until fragrant. Set aside.

Assemble

1. Spread the softened onion and garlic evenly across the bottom of the oiled baking dish.
2. Arrange the potato slices in a single overlapping layer on top of the onion base. Drizzle with 1/2 tbsp olive oil, season with 1/4 tsp salt and a few grinds of pepper.
3. Add an overlapping layer of zucchini slices. Season lightly with salt and pepper.
4. Finish with a top layer of tomato slices, slightly overlapping. Season with the remaining salt and pepper. Drizzle with the remaining 1/2 tbsp olive oil.

Herb Crust and Bake

1. In a bowl, combine the panko, Parmesan, rosemary, thyme, minced garlic, 2 tbsp olive oil, and 1/4 tsp salt. Mix until the crumbs look evenly coated and clump slightly when pressed.
2. Scatter the breadcrumb mixture evenly over the tomato layer. Press it gently with your palm so it adheres as a cohesive layer.
3. Bake uncovered at 200 C / 390 F for 40 to 45 minutes, until the crust is deep golden brown and the potatoes are tender when pierced with a knife tip.
4. If the crust is browning too fast before the 35-minute mark, lay a sheet of foil loosely over the top and remove it for the final 5 minutes.
5. Remove from the oven and rest for 10 minutes before slicing and serving. The vegetables will set and the layers will hold cleanly when cut.

Notes

For a crispier base, par-bake the potato layer alone for 10 minutes before adding zucchini and tomato. This ensures the potatoes cook fully without over-softening the top vegetables.

Tips for Success

• Slice all vegetables to a uniform 3 mm thickness so they finish cooking at the same time.
• Salt the zucchini slices 10 minutes before layering and pat dry to prevent a watery base.
• Press the breadcrumb mixture firmly onto the top layer so it bonds and crisps as a cohesive crust.
• Brush the baking dish with olive oil generously to help the bottom layer develop color rather than steam.
• Rest the gratin 10 minutes after pulling from the oven before slicing so it sets and holds its layers.

Variations

• Add 100 g sliced fennel between the potato layers for an anise-forward, Provencal-style gratin.
• Swap Parmesan for smoked cheddar in the crust for a deeper, more robust flavor profile.
• Layer in thin eggplant slices alongside zucchini for a heartier, more substantial vegetable base.

Storage and Reheating

Store leftovers covered in the fridge for up to 3 days. The crust softens overnight but firms back up when reheated properly.

To reheat, place portions on a baking sheet in a 180 C / 350 F oven for 10 to 12 minutes until the crust is crisp again. Avoid the microwave for the whole dish as it steams the breadcrumbs and kills the texture.

This gratin does not freeze well. The vegetables release water on thawing and the crust turns mushy, so make only what you plan to eat within a few days.

Serving Suggestions

Serve alongside roast chicken or grilled fish for a complete dinner. The acidity from the tomatoes cuts through richer proteins cleanly.

For a vegetarian meal, pair it with a lentil bowl with lemon and herbs dressed with olive oil. The crust and the beans together give you enough protein and substance to eat as a main.

At room temperature it also works well on a spread with other roasted vegetables on crusty bread, hummus, and olives for a casual weekend lunch.

FAQ

Why is my vegetable gratin watery at the bottom?

The most common cause is skipping the step of salting and drying the zucchini before layering. Zucchini and tomatoes both release a lot of liquid as they cook, and without drawing some out first, it pools at the base. Patting the slices dry with paper towels before assembling makes a noticeable difference.

Can I use regular breadcrumbs instead of panko for the herb crust?

Yes, regular dried breadcrumbs work but the crust will be denser and less airy than with panko. Keep an eye on it from about 25 minutes in since regular breadcrumbs tend to brown faster.

Can I assemble this herb crusted gratin the night before baking?

You can layer the vegetables and refrigerate the unbaked gratin for up to 12 hours. Add the breadcrumb topping right before it goes in the oven so it doesn’t absorb moisture overnight and lose its crunch.

What protein pairs well with herb crusted vegetable gratin as a dinner?

Roast chicken thighs or a simple baked white fish like cod or halibut are natural pairings. The herb crust echoes the seasoning on most roasted proteins and the tomato juices act as a light sauce.

Is herb crusted vegetable gratin gluten-free?

Not as written, since the crust uses panko breadcrumbs which contain wheat. You can make it gluten-free by substituting certified gluten-free breadcrumbs or using finely crushed almond flour mixed with Parmesan for the crust.

How is a vegetable gratin different from a vegetable tian?

A tian arranges sliced vegetables upright in overlapping rounds in the dish with no breadcrumb crust, and is closer to a straight roast. A gratin layers vegetables flat and finishes with a crisp, browned topping, which is the defining feature.