Heat the olive oil in a large skillet over medium heat. Add the Brussels sprouts and cook, stirring occasionally, until they are slightly browned, crispy on the edges, and tender in the middle, about 4–5 minutes.
Stir in the minced garlic and cook for an additional minute.
Lower the heat to medium-low. Add the heavy whipping cream, Parmesan cheese, kosher salt, black pepper, and red pepper flakes (if using). Cook, stirring frequently, until the sauce thickens, about 2–3 minutes.
Transfer the Brussels sprouts to a serving dish. Garnish with additional Parmesan cheese before serving.