Julia Child's Ground Beef Patties with Onions and Herbs (Bifteck Haché A La Lyonnaise)

Name: Julia Child's Ground Beef Patties with Onions and Herbs (Bifteck Haché A La Lyonnaise)
Prep time: 10 min
Cook time: 10 min
Total time: 20 min
Cuisine: American
Ingredients: 3/4 cup yellow onion, finely minced; 2 tablespoons butter; 1 1/2 lbs lean ground beef; 2 tablespoons butter, softened; 1 1/2 teaspoons salt; 1/8 teaspoon pepper; 1/8 teaspoon thyme; 1 egg; 1/2 cup flour, spread on a plate; 1 tablespoon butter; 1 tablespoon oil; 1/2 cup beef stock, beef bouillon, dry white wine, dry white vermouth, red wine, or 1/4 cup water; 2-3 tablespoons butter, softened; 2 tablespoons green herbs, minced (such as parsley, chives, tarragon, or chervil)