Place cauliflower in a steamer over a large pot of boiling water. Steam for 15 minutes until tender. Alternatively, boil cauliflower in salted water for 10 minutes or until fork tender. Remove and drain. Cover with a lid and set aside.

In the same pot, heat the butter over medium high heat. Sauté garlic until fragrant (about 1 minute).

Blend cauliflower and garlic in a food processor on high setting until smooth. You may need to do this in batches of two or three, depending on the size of your processor.

Transfer blended cauliflower into the pot with the garlic. Stir in the Parmesan cheese, sour cream and season with salt and pepper.