Hamburger buns are usually sold in packages of 8. You can substitute Kaiser rolls, which come in 6-packs, or purchase rolls individually from the bakery section of the supermarket.
1 1/2 lb ground beef
2 Tbsp sour cream
2 Tbsp ketchup
1 envelope of onion soup mix
1/2 cup cornflake crumbs
1 (4 oz) can mushrooms
1 Tbsp flour, divided
6 leaves of lettuce
6 hamburger buns
Combine ground beef, sour cream, ketchup, soup mix and cornflake crumbs in bowl; mix well. Mix mushrooms into the ground beef mixture.
Sprinkle half the flour onto waxed paper. Shape ground beef mixture into 6 patties; place on waxed paper. Sprinkle with remaining flour.
Preheat a heavy skillet sprayed with nonstick cooking spray. Sear patties on both sides. Reduce heat to medium. Cook, loosely covered, until cooked through, about 5 minutes per side.
Drain patties on paper towels. Assemble tomato, lettuce and patties on toasted buns. Serve immediately.
Dusting the burgers with flour creates a nice, even color when the patties are cooked. You could substitute finely crushed cornflake crumbs for a crunchier, more golden result.