Preheat the oven to 425°F (220°C).
Cut the bell pepper into small cubes, dice the onion, finely chop garlic.
Heat butter in a medium frying pan over medium-low heat. Add the bell peppers and onion. Cook for a couple of minutes until softened. Add garlic and cook for 30 seconds, until fragrant. Season with salt and pepper to taste. Transfer the vegetables to a bowl and chill in the fridge.
When the vegetables are chilled, take the puff pastry out of the fridge. Roll it out slightly into a rectangle then cut into 6 squares. See photos in the post for a reference.
Score each square creating a 1/2-inch (1cm) border (do not cut all the way through).
Place the squares on a baking sheet lined with parchment paper. Bake for about 16-17 minutes or until nicely golden in color.
Take the baking sheet out of the oven and reduce the temperature to 325°F (160°C). Using a spoon, press down the center of each pastry square.
Break an egg into each pastry square. Divide the vegetables around the eggs. Sprinkle with cooked crumbled bacon, crumbled feta cheese, and chili flakes (if using). Season the eggs with salt and pepper.
Bake until the egg whites are set but egg yolks still runny, about 15 minutes. Take out of the oven and sprinkle with finely sliced green onions.
Enjoy!