Heat olive oil and butter in a large skillet over medium heat. Add the prawns, season with salt and pepper, and cook for 2 minutes per side, or until they turn pink and opaque. Remove the prawns from the skillet and set aside.
In the same skillet, add 3 tablespoons of butter. Once melted, add the minced garlic and sauté for 2 minutes, until fragrant (being careful not to burn the garlic).
Pour in the heavy cream and stir to combine. Let the sauce simmer for 2 minutes to thicken slightly.
Stir in the grated Parmesan cheese and lemon juice. Let the sauce simmer for another 2 minutes, until the cheese is melted and the sauce becomes creamy.
Return the prawns to the skillet and toss them in the creamy garlic butter sauce. Cook for an additional 2 minutes to heat everything through and ensure the prawns are coated in the sauce.
Garnish with fresh parsley and serve hot, over rice or pasta.