These mouthwatering open faced Mushroom and Onion Steakburgers are an elegant way to serve a burger for a special meal or as an appetizer. Fresh hoagie rolls are slathered with garlic butter then topped with seasoned ground sirloin and baked until the beef is cooked. Top with sautéed mushrooms and caramelized onions they're ready to smother with cheese. Place under the broiler until the cheese is gooey and golden. Cut into pieces and serve with dippers as an appetizer, game day treat or a small bites meal.
Open Faced Mushroom and Onion Steakburgers
It's not often you'll hear the word elegant used in the same sentence as a burger. These steakburgers are just that, when served with basil pesto or sundried tomatoes on the side as a dinner or starter for a casual soiree. I enjoy serving them both ways, as an appetizer as well as a small bites meal. It's a sort of a grown-up way to eat an everyday cheeseburger and the buttered, garlicky, cheesy baguette makes it over the top gourmet good! In those moments I don't have time to grill, or the weather won't permit, these delectable open faced burgers curb the burger craving spot.

Tips for Making Steakburgers in the Oven
- The ground beef isn't precooked, it cooks in the oven. Due to This it's important to use a lean ground beef.
- The flavor will be directly affected depending on the quality of the steak seasoning used. Use a good brand that you already enjoy or one that's readily available on the spice aisle. Chicago and Montreal steak seasonings are both easy to come by.
- Use your favorite cheese for this recipe.
- Use a super sturdy baguette for the best end result
Other Ways to Enjoy Burgers
Cheeseburgers are always met with sheer joy at our house. They come in many forms. A few in the MSSK recipe index you may enjoy:
- Bacon Cheeseburger Crescent Ring
- Bacon Cheeseburger Pie
- Cheeseburger Soup
- You may also like to try these Smash Burgers from The Food Charlatan.
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Open Faced Mushroom and Onion Steakburgers
Servings: 8 servings
Calories: 458kcal
Ingredients
- 1 21 inch soft french baguette
- 4 tablespoon unsalted butter softened
- 1 teaspoon garlic salt
- 10-12 thick slices Gruyere or Cheddar cheese cut in half and divided
- 2 lb extra-lean ground sirloin
- 1 tablespoon steak sauce i.e. A-1
- 1 ½ teaspoon steak seasoning (i.e. Kansas City, Chicago or Montreal use your favorite)
- 1 large egg
- 2 tablespoon olive oil
- 1 8 oz container sliced baby portabella
- 1 large sweet onion thinly sliced
- 1 tablespoon balsamic vinegar
- 2 teaspoon fresh thyme leaves
- ¼ teaspoon sugar
- salt & black pepper to taste
Instructions
- Preheat the oven to 400°F and move the oven rack to the upper ⅓ of the oven. Line a large baking sheet with parchment.
- Slice the baguette in half, then cut each piece in half again making 4 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.
- 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.
- 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.
- Place burgers into the oven and bake for 20-22 minutes depending on the thickness of the meat. Remove from the oven, place the sauteed mushrooms and onions on top, then cover with the remaining cheese.
- Set the oven on broil, then return to the oven until the cheese melts.
- Cut each steakburger into 4 equal pieces and serve with an assortment of flavored mayonnaise, pesto or spreads.
Notes
- By moving the oven rack closer to the top element the meat will cook evenly without overcooking the baguette.
Nutrition
Serving: 1serving | Calories: 458kcal | Carbohydrates: 4g | Protein: 23g | Fat: 28g | Saturated Fat: 11g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 12g | Trans Fat: 1g | Cholesterol: 117mg | Sodium: 414mg | Potassium: 409mg | Fiber: 1g | Sugar: 3g | Vitamin A: 260IU | Vitamin C: 3mg | Calcium: 50mg | Iron: 3mg
Tried this recipe?Mention @melissassk or tag #melissassk!
Seasons01
Why don't you fry everything first... put on the bun then put in the oven to melt the cheese??
Patti
That’s what I would do
Lori @ RecipeGirl
Exactly the sort of thing my boys love me to make for dinner!
Melissa
It truly is "guy food" my boys gobble these up!
Tricia @ Saving Room for Dessert
My family would flip for these steak burgers - they look fantastic!
Melissa
Thanks Tricia!
Jane
Do you cut the bread in half length wise twice?
Melissa
Cut the bread through the middle prior to baking. Then into desired size pieces after baking.