Preheat the oven to 350°F
Mix the beef stock and 32 ounces water. Cook the shells according to the package instructions. Reserve 1/2 cup of the pasta water.
Melt the butter in an oven-proof skillet (see note to alternative), then add the bell pepper, onion, and garlic clove. Cook for 30 seconds.
Mix in the ground beef and season it with salt and pepper. Cook until tender. Drain the grease and return the heat to medium. Stir in the cream cheese until it is melted.
Mix the reserved cooking liquid, the noodles and the shredded mozzarella together.
Add sliced provolone. Bake for 20-25 minutes, or until the provolone has melted completely.