Preheat your oven to 375°F (190°C).
In a pot, bring water to a boil and add the cauliflower florets. Cook for about 5 minutes until tender and drain.
In a separate pan, heat the olive oil and butter over medium heat. Add the garlic and sauté until fragrant.
Stir in the milk and bring to a simmer. Gradually add the Parmesan cheese, stirring constantly until the sauce thickens.
Mix the cooked cauliflower with the alfredo sauce and season with salt and pepper to taste.
Transfer the mixture into a baking dish and top with shredded mozzarella cheese.
Bake in the preheated oven for 25-30 minutes, until the top is golden and bubbly.
Let it cool slightly before serving. Enjoy!