Cook the shell pasta in heavily salted boiling water until al dente, about 8 minutes. Reserve 1 cup of pasta water, drain, and set aside.

In a large skillet, cook diced pancetta over medium-high heat for about 5 minutes until crispy and golden brown. Transfer to a paper towel-lined plate to drain excess grease.

In the same skillet, melt butter over medium heat. Add diced onion and sauté until translucent (about 3 minutes). Add minced garlic and sauté for another minute until fragrant.

Stir in heavy cream and black pepper. Bring to a simmer and let thicken for about 5 minutes, stirring occasionally.

Add frozen peas and crispy pancetta back into the skillet. Fold in the cooked pasta, mixing until evenly coated. Adjust sauce thickness with reserved pasta water as needed.

Transfer to serving plates, garnish with parsley and Parmesan cheese, and serve hot.