Cook penne in a large pot of lightly salted water. Cook according to package, drain and set aside.
Add 1 tablespoon butter and olive oil in a large oven safe skillet and melt over medium heat. Add garlic and cook until lightly browned, about 30 seconds to 1 minute. Add shrimp and parsley and continue cooking, flipping the shrimp until shrimp turns a bright pink, about 4-5 minutes. Remove seasoned shrimp from the skillet, keeping any extra butter and olive oil in the skillet.
In the same skillet melt the remaining 2 tablespoons of butter. Add flour and whisk until smooth. Add in chicken broth and milk, adding a little bit at a time, while continuing to whisk until smooth. Add in lemon juice, salt and pepper and stir.
Add in parmesan cheese, along with 2 tablespoons of mozzarella cheese and continue to mix until cheese is completely melted and sauce thickens.
Add 3/4 of the shrimp and cooked pasta into the cheese sauce and mix to fully coat the pasta.
Place the remaining 1/4 of the shrimp on top, followed by sprinkling the remaining 2 tablespoons of mozzarella on top.
Bake for 10 minutes, or until cheese melts and lightly browns. Serve and enjoy!