In a large skillet, heat over medium-high heat and add bacon strips. Fry the bacon for about 5–7 minutes until crispy and golden brown. Transfer the bacon to a plate lined with paper towels to drain excess grease.

Crack the eggs into a mixing bowl and whisk with a splash of milk, salt, and pepper. In the same skillet over medium-low heat, melt the butter. Pour in the egg mixture and stir gently for about 3–4 minutes until softly set and slightly undercooked. Remove from heat.

Preheat your oven to 180°C (350°F).

Slice the croissants in half and place the bottom halves on a serving tray. Layer with scrambled eggs, followed by crispy bacon, cheese, spinach, and sliced tomatoes. Add avocado if desired.

Place the assembled sandwiches on a baking sheet and warm in the preheated oven for about 5 minutes until the cheese melts.

Remove from the oven and serve immediately alongside fresh greens or a fruit salad.