Mushroom Sliders - cooking recipe

Ingredients

1 pound lean ground beef, or more to taste
1 large egg
1 small onion, finely chopped
1 cup finely chopped mushrooms
1 teaspoon ground black pepper
1/2 teaspoon garlic salt
salt to taste
6 portobello mushrooms, or more to taste
1 green bell pepper, halved and seeded
1 red bell pepper, halved and seeded
1 yellow bell pepper, halved and seeded

Preparation

Preheat an outdoor grill for medium-high heat and lightly oil the grate.
Mix ground beef, egg, onion, and chopped mushrooms together in a bowl, seasoning with pepper, garlic salt, and salt as you mix. Form mixture into patties about 2 inches in diameter.
Grill patties on the preheated grill until browned and desired doneness is reached, 5 to 7 minutes per side. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).
Grill portobello mushrooms, green bell pepper, red bell pepper, and yellow bell pepper on the grill until tender, 3 to 5 minutes per side. Use 2 mushrooms and as the 'bun' for the burgers.