Preheat the oven to 400 degrees and bring a large pot of salted water to a boil (for the shells). While the water heats, melt 1 Tablespoon of the butter in a large skillet over medium high heat. Add the ground beef, salt, and pepper. Sauté for 2-3 minutes. Add the mushrooms. Sauté for another 2 minutes. Lastly, add the peppers, onions, garlic, Worcestershire, and ketchup. Cook until most of the water has evaporated from the vegetables. Set aside.
1 Tablespoon unsalted butter, 1 pound 90/10 ground beef, 1 teaspoon Morton kosher salt*, freshly ground black pepper, 5 ounces baby bella mushrooms, diced finely, 1 green bell pepper, diced finely, 1 onion, diced finely, 5-6 cloves garlic, minced, 1 Tablespoon Worcestershire, 1 Tablespoon ketchup
While the meat finishes cooking, cook the pasta for 1 minute less than the instructions on the package in salted water. (For reference, mine says to cook for 9 minutes, so I boil it for 8 minutes).
28 jumbo shells, about 8 ounces
In a medium saucepan, melt 3 Tablespoons of the butter over medium heat. Whisk in the flour until a smooth paste forms. Add the milk and whisk until the mixture begins to thicken and simmer.
3 Tablespoons unsalted butter, 1/4 cup all purpose flour, 2 cups nonfat milk
Turn the heat to low. Stir in the salt, American cheese, and shredded cheddar cheese. Continue stirring until the cheese is melted. Stir in the jalapeños.
1/2 teaspoon Morton kosher salt*, 4 ounces American cheese, sliced or cubed, 4 ounces (1 cup) sharp cheddar cheese, shredded*, 1/4 cup diced pickled jalapeños
Grease a 9 x 13 inch baking dish. Pour about 1 cup of the cheese sauce into the bottom. Stuff each shell with beef filling. Place into the dish.
Pour the remaining sauce on top.
Sprinkle the cheddar cheese cubes on top.
4 ounces sharp cheddar cheese, cubed*
Bake for 15-20 minutes or until the edges begin to bubble.