Heat oil in a large frying pan over medium-high heat. Add onion and garlic and season with salt and pepper. Cook, stirring occasionally, until translucent. Add ground beef, potatoes, and carrots, and season again with salt and pepper. Cook until beef is browned.

Add measured salt, cumin, paprika, beer, chicken broth, and epazote and bring to a simmer. Cook, uncovered, until liquid has cooked down and vegetables are tender, about 10 minutes. Set aside to cool. Once cooled, stir in the mint leaves. Picadillo can be made up to a day in advance.

Set a small pan of water over high heat and bring to a boil.

Remove stems from the dried chiles and remove as many seeds as possible. Rinse chiles under cold water removing the rest of the seeds.

Heat a large cast iron skillet or comal over medium-high heat. Place chiles on the hot, dry pan and toast until all the water has evaporated off the chiles and they are beginning to smell fragrant (about 4 minutes), turning frequently. Transfer chiles to the pan of boiling water, submerge under the water, and remove from heat. Set aside until very soft, at least 15 minutes.

Place tomatoes, onion quarters, and serrano chiles on the hot cast iron skillet over medium-high heat (you may need to do this in batches depending on the size of the skillet). Char the vegetables until they have blackened on all sides and are slightly softer, about 10 minutes. Remove stems from serrano chiles and remove seeds if you don't want the sauce to be spicy.

Pour chicken broth into blender then add drained dried chiles, and charred vegetables (you may need to do this in batches depending on the size of your blender). Add salt and blend on high until smooth. Sauce can be made up to 3 days in advance.

Heat oven to 400°F. Have 2 large plates and 2 (at least 7-x-11in) baking dishes near by.

Heat 1/4 cup of the oil in a large frying pan over medium-high heat. Using tongs, add tortillas, one at a time, and lightly fry each tortilla until slightly soft and a bit crisp on the edges, about 15 seconds per side. Transfer tortillas to one of the plate until all have been fried, adding more oil, 1 tablespoon at a time, if the pan becomes dry.

Once all the tortillas are fried there should be about 2 tablespoons of oil left in the pan, if not add enough to make 2 tablespoons or pour any extra into a heatproof container. Carefully add enchilada sauce to the pan (it will spatter) and stir until the spattering dies down. Let simmer about 5 minutes then turn the heat to very low.

Spoon enough sauce in the bottom of each dish just to coat.

Using tongs, dip one tortilla into the sauce and flip to coat in sauce. Transfer to the other large plate and place 2 tablespoons of picadillo on one edge. Roll tortilla around the filling then roll up to close. Lay enchilada in the baking dish and repeat with remaining tortillas and filling, coating each tortilla with sauce before filling and rolling it up.

Place twelve enchiladas in each baking dish then divide any remaining sauce over the two dishes, spreading it over the enchiladas.

If you are going to freeze one dish, cover the top tightly with plastic wrap, then cover the plastic wrap with foil. Place in freezer for up to one month. See post for instructions on how to bake from frozen.

To bake the enchiladas, place, uncovered in the hot oven until crispy on the edges and warmed through, about 15 minutes.

Serve immediately with a sprinkling of cheese and sour cream if you'd like and a few sliced chiles on top.