In a medium bowl, whisk together eggs, milk, salt, and pepper until well combined. Set aside.
Heat vegetable oil in a large nonstick skillet over medium-high heat. Add tortilla strips and cook, stirring occasionally, until golden and crispy, about 3-4 minutes. Transfer to a paper towel-lined plate.
In the same skillet, add onion, bell pepper, and jalapeño (if using). Cook over medium heat until softened, about 3 minutes.
Reduce heat to medium-low. Return tortilla strips to the skillet and spread evenly. Pour the egg mixture over the top. Let cook without stirring for about 30 seconds, then gently scramble with a spatula until eggs are just set but still moist, about 2-3 minutes.
Sprinkle cheese over the migas and remove from heat. Let sit until cheese melts, about 1 minute.
Serve immediately, garnished with cilantro, and with salsa and sour cream on the side.
Tips
For extra crunch, use day-old tortillas or fry the strips a bit longer.
Add cooked chorizo or bacon for a meatier version.
Serve with refried beans or a side of fresh fruit.