1 lb. ground beef
5 medium cremini mushrooms, sliced
1 medium yellow onion, thinly sliced
1/4 C water
3/4 C milk
3 T flour
2 oz shredded white cheddar cheese
4 pepperoncini, sliced crosswise
4 sandwich rolls
salt and pepper
Add olive oil to a saute pan over medium-high heat. Add the mushrooms and cook until brown, about 4 to 6 minutes. Add the onion and season with salt and pepper. Cook, stirring occasionally, 5 to 7 minutes, or until softened.
Add ground beef, salt and pepper to the vegetable mix. Cook, frequently breaking the meat apart, 3 to 5 minutes, or until meat is evenly browned. Add 2 tablespoons of water and cook, stirring frequently and scraping up any browned bits from the bottom of the pan. Remove from heat and set aside.
Add olive oil to a pot over medium-high heat. When the oil is hot, add the flour and cook, whisking constantly, 1 to 2 minutes, or until golden. Slowly whisk in the milk and water, turn heat to high and bring to a boil. Once boiling, reduce the heat to low and simmer, whisking frequently, 4 to 6 minutes, or until thickened. Add the cheese, season with salt and pepper. Whisk until thoroughly combined and sauce is smooth.
Slice buns down the middle, like a hot dog bun, and toast. Divide the beef mixture across the rolls, top with cheese sauce and pepperoncini.