Wendy's Bacon Portabella Mushroom Melt

Burger

14 oz. lean ground beef
1 tsp. seasoning salt, steak spice or to taste
6 cremini mushrooms, sliced
1 Tbsp. butter plus more for buttering the buns
6 strips applewood smoked bacon, cooked crisp
4 cheddar cheese slices
2 brioche buns
Salt and pepper to taste

Cheese Sauce

2 Tbsp. butter
2 Tbsp. flour
1 cup milk
1 cup aged cheddar cheese, grated
Salt to taste
pinch of cayenne

Mix the salt with the beef and form into two patties. Set aside. Melt the butter in a small fry pan and saute the mushrooms over medium heat. Season with salt and pepper. Set aside.
Meanwhile add the butter to a small saucepan and stir in the flour, cook for 1 min. Slowly add in the milk whisking. Bring the sauce up to a simmer and let thicken. Add the cheese, salt to taste and cayenne, stir well until cheese melts. Set aside keeping warm.
Heat the BBQ to 425 using a flat top or cast iron pan. Cook the burgers for 4-6 min per side or until internal temperature is 160-165F.
Butter the brioche buns and toast on the flat top or grill.
To assemble the burger place a cheese slice on the bottom of the two buns, top with the patty, then the second cheese slice followed by the bacon, cheese sauce and mushrooms and the top of the bun.