Prep the Ingredients: Gather all ingredients. Ensure the fish is fresh and boneless.
Melt the Butter: In a pan, heat 2 tablespoons of unsalted butter over medium heat.
Cook the Shallots: Add the finely diced shallots and cook until they are soft and fragrant.
Add Lemon Juice: Pour in the lemon juice and slowly add the remaining butter until fully melted.
Poach the Fish: Place the fish in the pan, making sure it's covered by the butter mixture. Keep the butter between 150°F and 170°F, ensuring it doesn’t boil.
Cook Gently: Cook the fish until it's tender and cooked through. Thinner fillets will take under 10 minutes, while thicker ones may take up to 20 minutes.
Season and Serve: Once done, season with salt to taste. Garnish with fresh herbs and serve immediately.