Preheat your oven to 350°F (175°C). Grease a standard muffin tin with cooking spray or lightly brush it with oil. This will help prevent sticking. If you have silicone muffin molds, those are fantastic, too!

In a medium skillet, melt the unsalted butter over medium heat. Add the chopped onions and sauté for about 3-4 minutes until they soften. Toss in the chopped mini bell peppers and continue cooking for another 3 minutes. Lastly, add the spinach and cook until just wilted. That should take about 2 more minutes. Remove from heat and set aside.

While the veggies are cooling, crack the eggs into a large mixing bowl. Add sea salt, black pepper, and red pepper flakes. Whisk vigorously until the mixture is well combined and slightly frothy. This will create a light and fluffy texture for your muffins.

Once the vegetable mixture has cooled slightly, fold it into the whisked eggs. Gently mix in the heavy cream and the crumbled feta cheese. Be careful not to overmix; you want to keep some of that feta intact.

Spoon the egg and veggie mixture evenly into each muffin cup. Fill them about two-thirds full to allow some room for rising.

Pop your muffin tin into the preheated oven. Bake for 18-20 minutes or until the muffins are puffed and a toothpick inserted in the center comes out clean. The tops will be lightly golden.

Once baked, let them cool in the pan for about 5 minutes. Then, use a butter knife to gently pry the muffins away from the sides. Transfer to a wire rack to cool further. Garnish with fresh chives if you’d like!