Preheat your oven to 350°F. While the oven heats, prepare all your ingredients: dice the onion and red bell pepper into uniform 1/4-inch pieces, chop the roasted green chiles, shred the Monterey Jack cheese, cut the corn tortillas into strips, and finely chop the fresh chives for garnish. Having everything prepped and ready before you start cooking ensures the assembly process moves quickly and smoothly.

Heat the olive oil in a large skillet over medium-high heat. Add the breakfast sausage and cook for 4-5 minutes, breaking it apart as it cooks until it's completely browned and crumbled. Add the diced onion and red bell pepper, cooking for another 1-2 minutes until the vegetables just begin to soften. Season generously with salt and black pepper, then stir in the chopped green chiles. Remove from heat and set aside—this flavorful filling is the foundation of your casserole.

In a bowl, whisk together the room-temperature eggs and milk until well combined and slightly frothy. This creates a silky custard that will bind everything together. Add the paprika and red pepper flakes, whisking to incorporate the spices evenly throughout. I like to season the egg mixture at this point with a small pinch of salt so the flavors are balanced throughout the casserole.

Lightly oil or butter a 9x13-inch baking dish. Start with a layer of tortilla strips on the bottom, then add a portion of the sausage mixture from Step 2, followed by a handful of shredded cheese. Pour about one-third of the egg custard from Step 3 over this layer. Repeat this layering process two more times (tortilla strips, sausage mixture, cheese, egg custard), then finish with a final layer of tortilla strips on top. This creates even distribution of flavors and textures throughout the casserole.

Transfer the assembled casserole to the preheated 350°F oven and bake for 35 minutes, until the egg custard is set but still slightly jiggly in the very center when you gently shake the dish. The top should be lightly golden. Remove from the oven and let it rest for 5 minutes before serving—this allows the residual heat to finish cooking the center and makes it easier to cut clean portions.

Sprinkle the fresh chopped chives over the warm casserole just before serving. The bright, mild onion flavor of the chives provides a fresh counterpoint to the rich, spiced eggs and savory sausage filling.