Begin by bringing a large pot of salted water to a rolling boil. Add the medium uncooked shells and cook according to package instructions, about 8-10 minutes, until al dente. Drain and set aside.

In a large skillet, heat olive oil over medium heat. Add the chopped onion and sauté for about 5 minutes, until golden and translucent.

Add the lean ground beef and break apart with a spoon. Cook for about 5 minutes, stirring occasionally until browned.

Stir in the minced garlic and chili powder, cooking for another minute until fragrant.

Add the tomato sauce and beef broth to the mixture and stir well. Reduce heat to low and simmer for about 4-5 minutes until thickened.

Pour in the heavy cream, stirring gently to achieve a creamy texture. Season with salt and pepper to taste and warm through for 2-3 minutes.

Add the cooked pasta shells back into the skillet, tossing to coat with the creamy sauce. Cook for another minute over low heat.