Making the Breakfast Frittata Sandwich is a simple yet rewarding experience. Follow these steps to create this delicious meal:

1. Preheat and Prep: Preheat your oven to 350°F (175°C).

2. Prepare the Vegetables: In a skillet, heat the olive oil over medium heat. Add the chopped onions and bell peppers. Sauté until soft, about 5 minutes. Stir in the spinach and cook until wilted, about 2 minutes.

3. Mix the Egg Mixture: In a large bowl, whisk together the eggs, milk, salt, and pepper. Make sure it’s well mixed.

4. Combine Veggies and Eggs: Add the sautéed vegetables to the egg mixture. Stir well to combine.

5. Add Cheese: Fold in the shredded cheese gently, ensuring it is evenly distributed.

6. Bake the Frittata: Pour the mixture into a greased baking dish. Bake in the preheated oven for 20-25 minutes, until the frittata is set and slightly golden on the edges.

7. Cool and Slice: Remove the frittata from the oven and allow it to cool for a few minutes. Once cool enough to handle, slice it into squares.

8. Toast the Bread: While the frittata is cooling, toast the bread slices until golden brown.

9. Assemble the Sandwich: Place a slice of frittata between two pieces of toast. Add optional toppings like avocado, salsa, or hot sauce if desired.

10. Serve Warm: Enjoy your Breakfast Frittata Sandwich warm for the best flavor.

By following these steps, you’ll create a delicious Breakfast Frittata Sandwich that is sure to satisfy!