Preheat the oven to 450 degrees F. Spread the butter in the cups of a 12-cup muffin tin.
Heat the oil in a large skillet over medium heat. Add the garlic and sauté for 1 minute. Add the spinach, cover the pan, and cook until the spinach is wilted. Add the roasted red peppers and sauté for 1 minute. Transfer the mixture to a strainer and drain off the excess liquid.
Layer each prepared muffin cup with 2 slices prosciutto, creating a cup shape. Divide the spinach mixture evenly among the cups.
Crack an egg into each cup. Add a pinch of salt and pepper on the egg.
Bake for 10–15 minutes. Allow to cool for 5 minutes, then gently remove the egg cups from the muffin tin. Garnish with the chives. Serve 2 egg cups to each person with 1 slice toast, cut into 2 triangles.
