Preheat the oven to 400°F.
Prepare croissant sandwiches: Line a large sheet pan with parchment paper. Slice the croissants in half and place them on the sheet pan.
Top each croissant with 2-3 slices of cooked bacon (add more if you like).
Crack eggs, milk, salt, and pepper into a large bowl. Whisk vigorously until the eggs are frothy and smooth.
Over medium heat, melt butter in a skillet. Do not let the butter bubble or it may burn. Swirl the pan so that the butter coats the entire skillet.
Pour the eggs into the skillet and let them sit undisturbed until lightly set.
Take your spatula or whisk and stir gently, then push the eggs to the edge of the skillet. Let the eggs set again. Repeat until the eggs begin to curdle.
Add shredded cheese over the eggs (sliced cheese works too). Gently stir the eggs into the cheese but not too much that the cheese disappears into the eggs.
To prepare the croissant sandwich, place equal amounts of eggs onto each croissant. Top with a bit more shredded cheese if you like.
Place the other half of the croissant on top and bake for 5-10 minutes or until the cheese is melted.