Cook bacon in a large skillet over medium heat for 4-5 minutes per side until crispy. Transfer to paper towels to drain. Reserve 1 tablespoon of bacon drippings in the pan.

Toast the cut sides of the croissants in the bacon drippings over medium heat for 1-2 minutes until golden. Remove and set aside.

Add butter to the same pan over medium heat. Crack eggs in and season with salt and pepper. Cover with a lid and cook for 2-3 minutes until whites are set and yolk is still runny (or to your liking).

Immediately place a slice of cheese on each hot egg and let it melt for 30 seconds.

Layer the bottom of each croissant with 2 strips of bacon, then top with the cheesy egg. Add hot sauce or mustard if desired. Cap with the top of the croissant and serve immediately.