Heat your oven to 350°F (175°C).
Arrange the croissants cut side facing up on a baking sheet.
Toast the croissants in the oven for 5 to 7 minutes until slightly crisp.
While toasting, melt butter in a skillet over medium heat.
Beat the eggs in a bowl until smooth and combined.
Pour the eggs into the skillet once the butter bubbles.
Gently stir the eggs every so often and cook for 3 to 4 minutes until fully scrambled.
Season the eggs evenly with salt and black pepper and mix well.
Remove the skillet from heat once eggs are cooked.
Cut each croissant horizontally into halves.
Place a slice of cheddar on each bottom croissant half.
Layer one cooked bacon slice on the cheese of every croissant bottom.
Evenly distribute the scrambled eggs on top of the bacon.
Add a small amount of spinach over the eggs.
Carefully cover with the top croissant halves to assemble sandwiches.
Serve right away while croissants remain warm and cheese has started to melt.