Slice one onion and chop the other. Throw some slices into crock pot to cover bottom. Throw in 4-5 Brats. Add more slices of onion. Continue until all brats are in the pot.
Top off brats with any left over sliced onions. Pour in 4 cans of Stout beer. Add cheap beer so that brats are submerged.
Add in butter and oil. Turn crock pot on low for 6-8 hour cook or high for 3-4 hour cook. Remove brats from crock pot. They should be gray and plump. Throw on Egg at 300-350 and let them soak up the smoky flavor and char slightly.
Take onions from crock pot and fry. Take brat's off, put them in buns, cover with raw chopped onions, fried onions and mustard.