Mushroom Swiss Patty Melt with Caramelized Onions

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patty melt 3


This is an amazing way to use up leftover burgers or meatloaf (the photo above used leftover meatloaf)… but completely worth cooking it up fresh!  Caramelizing the onions is a slow process but adds a beautiful sweet & rich flavor to the burgers!

While rye is the traditional choice for a patty melt, I really enjoy the flavor and texture of sourdough so that’s what I used!

Mushroom Swiss Patty Melt

Author Holly


  • 8 Slices Sourdough Bread (or rye bread)
  • Grainy Mustard (optional)
  • 16 Slices Swiss Cheese
  • 12 Large Mushrooms , sliced
  • 1 teaspoon soy sauce
  • 2 Onions , sliced
  • 1/2 tablespoon brown sugar
  • Butter
Hamburger Patties
  • 1 lb . Lean Ground Beef
  • 2 tablespoons finely chopped onion
  • Pepper
  • Frozen burger patties
  • Left over meatloaf or hamburgers
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    1. Over low heat, combine sliced onions, 1 tablespoon of butter and brown sugar.
    2. Slowly cook onions stirring until golden. This can take a up to 25 minutes… but they can cook slowly while you prepare the rest of the ingredients.
    Beef Patties
    1. If using frozen patties, cook according to package directions. For fresh beef, combine beef, onion and pepper. Divide into thin 4 patties (remember they will shrink in size a bit when cooked).
    2. Over medium-high heat, cook the patties 2 at a time for 3 minutes on each side until no pink remains. Set aside.
    1. Toss sliced mushrooms with soy sauce and cook over medium high heat until juices have been released. Set aside.
    Patty Melt Assembly
    1. Lightly butter both sides of the bread slices. On a griddle or frying pan, grill the bread on one side until lightly browned. Remove from heat.
    2. On the already grilled side, spread a very thin layer of grainy mustard. Create your sandwich adding the ingredients in this order: 1 slice cheese, onions, meat patty, mushrooms, slice of cheese, bread
    3. Grill on medium low heat until bread is browned and cheese is melted.
    4. Enjoy!
    Nutrition Information

    (Nutrition information provided is an estimate and will vary based on cooking methods and brands of ingredients used.)

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    About the author


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    Holly is a wine and cheese lover, recipe creator, shopping enthusiast and self appointed foodie. Her greatest passion is creating in the kitchen and making deliciously comforting recipes for the everyday home cook!

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    1. OMG Yum is the word for your Mushroom Swiss Patty Melt!!!! I’m doing it this week for my son who will be over the moon!!!! Thank You!!!!