To a food processor, add - oregano, cumin, chili powder, salt, black pepper, garlic, olive oil, white wine, vinegar, brown sugar, and onion. Blend until totally combined.
Pour over pork shoulder and rub it in.
Place into a roasting pan or dutch oven and add 2 cups of water. Cover tightly and roast for several hours (3-6), turning once every hour.
When pork is fork tender (and falling apart), remove the lid and roast it, skin sdie up for another 15-20 minutes to get the skin crispy. (This is not a necessary step - and if I don't have time, I don't do this)
Let rest for 15 minutes before shredding. Remove fat from top of shoulder before shredding.
I let the juice cool, and skim off the fat. The pour juices over shredded pork.
Serve on buns or with warm tortillas.
You can also add EL PATO brand Tomato Sauce. Usually found in the mexican food section of the grocery store. For a little heat and tomato flavor.
I have also started this in the oven @ 400 degrees for the first hour to hour and a half, then turned it down to 325 to shorten the cooking duration.