Preheat oven to 325°F.
In a heavy pot, heat vegetable oil over high heat.
Add pork and season with salt and pepper.
Brown on all sides.
Remove from pan and lower the heat.
Add onion, garlic, spices and tomato paste.
Sauté for a few minutes.
Add beer to the pan and scrape up browned bits on the bottom of the pot.
Return the browned pork and add the tomatoes.
Bring to a simmer.
Cover and move pan to the oven.
Cook for 1 1/2 hours.
While the pork is cooking, mix together all the masa dough ingredients.
Add a large dollop of dough to each opening in a muffin tin.
Press along the bottom and up the sides of the muffin tin.
Set aside until ready to use.
Once the pork is done, use forks to pull the meat apart.
Add some of the pork to each muffin tin, dividing the filling evenly.
Bake for 20-25 minutes.
Remove from the oven and allow to cool slightly.
Run a knife around the edges of the crust.
Garnish with sour cream, cilantro and queso fresco.