Bring a large pot of salted water to a boil. Add the sweet potatoes and cook until tender, about 15-20 minutes. Drain well.

Meanwhile, melt the butter in a skillet over medium heat. Add crushed garlic and sauté until fragrant, about 1-2 minutes.

Return the drained sweet potatoes to the pot. Add the sautéed garlic and butter, milk, and sour cream. Mash until smooth and creamy. Season with salt and pepper to taste.