Preheat the oven to 375 degrees F (190 degrees C).
Place bacon in a large skillet and cook over medium-high heat, turning occasionally, until evenly browned and crisp, about 10 minutes. Drain bacon on paper towels.
Fill a large pot with lightly salted water and bring to a rolling boil. Cook fettuccine at a boil until tender yet firm to the bite, about 8 minutes. Drain in a colander and rinse with cool water. Transfer to a bowl.
Add 1/2 the Parmesan cheese, 1/2 the mozzarella cheese, and ground pepper to the bowl with the pasta and toss. Layer 1/2 the pasta mixture into a baking dish. Top with 1/2 the cooked bacon and 1/2 the peas. Repeat layers of pasta, bacon, and peas. Top with remaining Parmesan cheese, mozzarella cheese, and butter. Pour heavy cream on top.
Bake in the preheated oven until hot and bubbly, about 45 minutes.
