In a large skillet, heat the olive oil and 1 tablespoon butter over medium heat. Add the cauliflower and sauté until it’s tender, 8 to 9 minutes. Add the garlic and toss until fragrant, 1 minute. Season with salt and pepper.
In a medium saucepan, heat the remaining 3 tablespoons butter over medium heat. Add the flour and cook, stirring constantly, for 2 minutes.
Whisk the milk into the saucepan and bring the mixture to a simmer over medium heat—the sauce should noticeably thicken. Remove the mixture from the heat and stir in the Pecorino. Season generously with more black pepper.
Stir the cauliflower into the sauce. Serve immediately.
