Preheat your oven to 350 degrees Fahrenheit. This step is crucial as it ensures your egg cups cook evenly.
In a large skillet, heat the avocado oil over medium-high heat. Once hot, add the chopped onion. Sauté for about 2 to 3 minutes until the onion begins to soften and becomes fragrant.
Add the finely chopped bell pepper and spinach to the skillet. Stir them together, cooking until the spinach has wilted down and all the veggies are tender.
Next, stir in the chopped chicken and sun-dried tomatoes. Cook for another minute or so, allowing the flavors to meld together.
Prepare a muffin tin by spraying the holes with cooking spray to make it easier to remove the egg muffins later.
Divide the spinach and chicken mixture evenly among the 12 muffin holes. Use a spoon to pack it down gently.
In a separate bowl or measuring cup, whisk together the eggs and egg whites. If you’d like, add seasonings like salt, pepper, or dried herbs for extra flavor.
Pour the beaten eggs into each muffin hole, filling them about three-quarters full. This will allow the eggs to puff up as they bake.
Sprinkle the tops of each muffin hole with feta cheese. This adds a creamy, tangy flavor that pairs wonderfully with the eggs.
Place the muffin tin in the preheated oven and bake for 20 to 25 minutes. They’re done when the muffins are fully cooked through and slightly golden on top.
If you have a meat thermometer, check that the internal temperature has reached 190 degrees Fahrenheit.
Once baked, allow the mini frittatas to cool in the pan. Run a butter knife around the edges of each muffin before gently releasing them.
Serve the egg muffins while warm, or let them cool completely before storing. Enjoy these Chicken and Spinach Egg Cups as part of a hearty breakfast!