Coat the roast with the garlic powder, paprika, pepper and salt. Sprinkle it all over as evenly as you can.
Using a preheated pan (Medium High) with the butter, brown on all sides.
If you are using a soup pot to cook this (not a slow cooker) add your beer, chicken stock and onion and simmer for three hours. Turn once during that time.
If you are using a slow cooker, add the browned roast and liquids (with onion) and put on low setting.
When the roast is ready, you will need to strain the fat and chunks from the liquid. We use a fat strainer but you can also use a ladle. It doesn't have to be perfect. Some fat is always ok and some bits of meat and onion won't hurt it either. Once you have strained this put aside.
Now we need to make a rue. Add 2 tablespoons butter over medium heat and let melt. Then add 2 tablespoons flour and whisk. As it becomes bubbly add in your liquid slowly. It will thicken quickly. You should have about a cup of strained liquid.
Keep going with the whisk for about 2 minutes. Add the milk and let sit another 2 minutes. Stir often.