This simple sheet pan dinner is easy and versatile. Throw any kind of fish, veggies and potatoes onto your pan, make an easy but magical 3 ingredient brown butter sauce on the side and dinner is ready!
On a large (half-sheet) sheet pan, toss the halved potatoes with one tablespoon of olive oil and sprinkle with a large pinch of salt and pepper. Bake in the preheated oven for 15 minutes, until almost tender, tossing once.
Remove the pan from the oven and toss the potatoes to one side. Add remaining tablespoon of olive oil to the other side of the pan and spread it around. Add the fish filets and green beans, spreading things out in one layer, as much as possible. Sprinkle with salt and pepper, and a little olive oil if desired. Return to the oven and bake for an additional 10-15 minutes, until the fish flakes easily with a fork. (This may take more or less time depending on the type of fish used).
Brown Butter Sauce
While things are in the oven, make the sauce. Melt the butter over medium heat in a light-colored saucepan or skillet. Swirling the pan occasionally, cook until the butter solids begin to brown at the bottom of the pan and the butter turns golden and starts to smell nutty. Remove from heat immediately and transfer to a small bowl or measuring cup.
Add zest of one lemon and 3 tablespoons of lemon juice, and mustard. Whisk or blitz with an immersion blender until emulsified. Season with salt and pepper to taste. Pour over plated fish and vegetables. It is a rich sauce, so use judiciously ;).