Preheat oven to 350°F. Grease a 9x13-inch casserole dish.
Line a baking sheet with foil and arrange seasoned beef meat strips on top if reheating.
In a large bowl, whisk eggs, milk, diced peppers, green onion, cilantro, ½ cup shredded cheese, and black pepper.
Pour egg mixture into the prepared casserole dish.
Place the egg dish in the oven and bake 15–20 minutes until eggs are set. Warm the seasoned beef meat strips in the oven during the last 5–7 minutes if needed.
During the last 3–4 minutes, add English muffins to the oven to toast lightly.
While baking, prepare the chipotle sauce: Blend chipotle pepper, adobo sauce, garlic, yogurt, and cilantro until smooth. Season with salt to taste.
Cut the baked egg mixture into circles sized to fit the English muffins.
Assemble the Spicy Chipotle Egg Breakfast Sandwiches: Place one egg round on the bottom half of each toasted English muffin. Sprinkle remaining cheese, add a generous spoonful of chipotle sauce, top with seasoned beef meat strips, and garnish with cilantro. Cover with the top muffin half and serve warm.
Notes
You can use grilled steak slices, seasoned ground beef patties, or deli-style roast beef.