Drunken Garlic Pot Roast

Bunky Mikrut was asking for a "real" pot roast recipe (featuring beef), as opposed to the previous one (Garlic Pot Roast) which was made with pork. So this is a recipe sent by JadeMarie, enjoy:

Don't be afraid of all the garlic in this! It gets really mild from the long cooking process and gives the meat a wonderful flavor.

2 1/2 lbs boneless beef chuck roast, trimmed of fat
2 tablespoons vegetable oil
1/2 teaspoon salt
1/4 teaspoon pepper
2 medium onions, thinly sliced
24 cloves garlic, minced (about 4 tbsp.)
2 beef bouillon cubes
1/2 cup hot water
8 ounces lager beer
3 tablespoons brown sugar
1 tablespoon Dijon mustard
1 tablespoon cider vinegar
cornstarch (dissolved in water; for gravy)

In a large skillet, heat 1 tbsp. of the oil and brown roast on both sides, seasoning with salt and pepper; remove to a platter and keep warm.
Add the remaining tbsp of oil to the pan and add the onions, cook until they just start to wilt then add the garlic, then cook until the onions are tender, a few minutes more.
Add the bouillon cubes to the hot water and stir to dissolve; add that to the skillet along with the beer, brown sugar, mustard, and vinegar; stir to mix well.
Pour mixture into the bottom of the crockpot.
Place roast on top of liquid, cutting into pieces if it doesn't lay flat.
Set the crockpot on low and cook for 7-8 hours.
Remove meat from crockpot and pour liquid into a pan on the stove; heat to a boil, and mix a slurry out of the cornstarch and water; thicken pan liquid with slurry to make a gravy.
Serve gravy over meat or with potatoes or noodles.