Slice the croissants in half, reserving the tops and breaking up the bottom portion.
Melt the butter over medium heat.
Sautee the garlic and white onion until fragrant and translucent.
Beat the eggs with the milk until frothy.
Layer the torn croissant pieces, egg mixture, cheese, dill, salmon, garli/onion and sliced scallions in a non-stick oven pan sprinkling each layer with fresh black pepper and salt. Top the casserole with the croissant tops, pressing them into the casserole so that they moisten.
Bake in the preheated oven until the eggs are done and the croissants are browned. Serve hot.