Open Faced Mushroom and Onion Steakburgers

Course Appetizer, Main Course

Cuisine American, Southern

Keyword mushroom-cheeseburger-recipe, open-faced-mushroom-onion-steakburgers, steakburgers

Prep Time 10

Cook Time 22

Total Time 32

Servings servings

Calories 458kcal

Author Melissa Sperka

1 21 inch soft french baguette
4 Tbsp unsalted butter softened
1 tsp garlic salt
10-12 thick slices Gruyere or Cheddar cheese cut in half and divided
2 lb extra-lean ground sirloin
1 Tbsp steak sauce i.e. A-1
1 1/2 tsp steak seasoning i.e. Kansas City, Chicago or Montreal use your favorite
1 large egg
2 Tbsp olive oil
1 8 oz container sliced baby portabella
1 large sweet onion thinly sliced
1 Tbsp balsamic vinegar
2 tsp fresh thyme leaves
1/4 tsp sugar
salt and black pepper to taste

Preheat the oven to 400°F and move the oven rack to the upper 1/3 of the oven. Line a large baking sheet with parchment.
Baguettes: Slice baguette in half lengthwise then cut each piece in half again making 4 even oblong pieces. Arrange side by side on the baking sheet. Divide butter between pieces and sprinkle lightly with garlic salt. Arrange half of the cheese slices over the buttered baguette reserving the other half for the top. Set aside.
Burgers: In a medium size mixing bowl, mix together ground sirloin, steak sauce, steak seasoning and egg. Mix until fully combined. Divide evenly between the baguettes, spreading to the edges. The meat will be thin.
Place burgers into the oven and bake for 20-22 minutes depending on the thickness of the meat.
Mushrooms and Onions: Meanwhile, while steakburgers bake, in a large skillet over medium-high heat, cook mushrooms and onions in a couple of drizzles of olive oil for about 10 minutes until golden. Add balsamic vinegar, fresh thyme and sugar. Season with salt and black pepper to your taste.
Set the oven temperature to broil and remove steakburgers from the oven. Arrange sauteed mushrooms and onions on top dividing evenly between the four pieces. Cover mushrooms with the remaining slices of cheese. Return to the oven broiling until the cheese melts.
Cut each steakburger into 4 equal pieces and serve with an assortment of flavored mayonnaise, pesto or spreads.

By moving the oven rack closer to the top element the meat will cook evenly without overcooking the baguette.