Slice the courgettes lengthwise into 5 mm planks, then halve the planks crosswise. Toss them with 1 tbsp olive oil until lightly coated.

Heat a 30 cm / 12-inch cast-iron grill pan over medium-high heat for 3 minutes. Grill the courgette in 3 batches, 2 minutes per side, until deep grill marks show and the slices bend without snapping. Move each batch to a cutting board.

Let the grilled courgette cool for 10 minutes, then chop it into 5 mm pieces. Press the pieces between two layers of paper towel to blot surface moisture. You should have about 400 g.

While the courgette cools, heat the oven to 120 C / 250 F and set a wire rack over a 33 x 46 cm / 13 x 18 inch sheet pan. Stir together the Greek yogurt, grated garlic, 1 tbsp lemon juice, and 1/8 tsp salt, then refrigerate until serving.

In a 2.5 L / 10-cup bowl, whisk the eggs, flour, baking powder, 1/4 tsp salt, black pepper, and lemon zest until smooth. Fold in the chopped courgette, feta, spring onions, mint, and dill. The batter should mound on a spoon.

Heat 1 tbsp olive oil in a 30 cm / 12-inch nonstick skillet over medium heat for 1 minute. Drop in 4 scoops of batter, about 1/4 cup / 60 ml each, leaving 2 cm between them, and flatten gently to 1.5 cm thick.

Fry for 3 minutes per side, without moving them, until the crust is deep golden and the center feels firm when pressed. Transfer the fritters to the rack in the oven.

Repeat with the remaining oil and batter in 2 more batches of 4, wiping out the skillet if any bits have darkened. Serve warm within 20 minutes, with the yogurt sauce and a scatter of mint.