Preheat the oven to 350°F (175°C).

Fill a pot with water, add a pinch of salt, and bring to a boil. Cook the cauliflower florets for about 5-7 minutes until tender but not mushy.

Drain the cauliflower in a colander and let it cool slightly.

In a large mixing bowl, combine the sour cream, milk, garlic powder, onion powder, salt, and pepper. Whisk until smooth.

Add the drained cauliflower to the sauce and gently fold until all pieces are coated.

Stir in 1 1/2 cups of shredded cheddar cheese into the mixture.

Pour the cauliflower mixture into a greased 9x13 inch baking dish and spread it evenly.

In a small bowl, mix the breadcrumbs with melted butter and the remaining cheese. Sprinkle this mixture evenly over the casserole.

Bake in the preheated oven for 45 minutes until golden and bubbly.