Use wooden spoon to beat until mixture is well-mixed.
Shape into 1 1/4-inch balls; handle gently and rinse hands often in water to keep mixture from sticking. (Easiest way to make them is to use small 1 1/4-inch diameter ice cream scoop, then gently shape with moistened hands.
Alternately, use tablespoon and moistened hands to shape mixture into balls.)
Arrange meatballs in single layer on lightly oiled baking sheet.
Refrigerate until firm, about 2 hours.
Heat 1 tablespoon butter and 1 tablespoon oil in 12-inch nonstick skillet over medium-high heat.
Add meatballs in batches, without crowding.
Cook until browned, shaking pan occasionally, about 5 minutes.
Transfer to wide, shallow, oven-to-table casserole.
Repeat with remaining meatballs, adding more butter and oil as needed.
Reserve hot skillet, unwashed, for making gravy.
Add onion to reserved skillet.
Cook over medium heat until softened, stirring often, about 4 minutes.
Add flour; cook 1 minute.
Stir in consomme.
Stir until thickened, about 4 minutes.
Stir until hot.
Taste and season with salt and pepper.
Strain gravy and pour over meatballs.
Cover casserole with lid or foil.
Bake at 300 degrees, shaking several times to shift meatballs, until just heated through, about 45 minutes.
Cool 20 minutes.
Use slotted spoon to set meatballs aside; skim fat from gravy.
Put meatballs back in gravy.
Reheat at 300 degrees until hot, 10 to 20 minutes.
(Can be refrigerated up to 3 days or frozen for 1 month. Let come to room temperature before reheating. Reheat, covered, in 300 degree oven until hot, about 45 minutes to 1 hour.).