Roast poblano peppers over an open flame or under the broiler until the skin is blackened.
Place the peppers in a paper bag and let them steam for 10 minutes.
Peel and remove the seeds from the peppers, then chop them.
In a skillet over medium heat, sauté the onion and garlic in olive oil until softened.
Add the chopped poblano peppers, diced tomatoes, vegetable broth, heavy cream, cumin, and salt. Bring to a simmer and cook for 10 minutes, or until slightly thickened.
While the sauce is simmering, whisk together the eggs, milk, salt, and pepper in a bowl.
In a separate skillet, scramble the eggs over medium heat until cooked through.
Spread a thin layer of poblano sauce in the bottom of the baking dish.
Warm the tortillas in the microwave or a dry skillet for a few seconds until pliable.
Fill each tortilla with the scrambled eggs, potatoes, and cheese. Roll them up and place them seam-side down in the baking dish.
Pour the remaining poblano sauce over the enchiladas.
Bake for 20 minutes or until the cheese is melted and bubbly.
Notes
You can add other fillings to your enchiladas, such as cooked chorizo, black beans, or corn.
If you don't have poblano peppers, you can use roasted bell peppers instead.
You can make the poblano sauce ahead of time and store it in the refrigerator for up to 3 days.