In large pot or Dutch oven, melt 2 tablespoons butter with canola oil. Add
roast; brown well on all sides. Remove roast from pan; set aside.
Add onions and minced garlic to drippings; saute until golden brown. Return
roast to pot. Add salt, pepper and beer.
Cover; let simmer for 2 to 2 1/2 hours, adding water if it becomes too dry.
Toward end of cooking time, remove remaining 2 tablespoons butter from
refrigerator and let soften.
When roast is tender, remove to a cutting board. Combine softened butter and
flour, then slowly stir mixture into gravy to thicken, using as much as is
necessary. Stir in cognac; let simmer while you carve the roast, then serve.