This mashed cauliflower recipe is a delicious low carb or keto alternative to mashed potatoes. It'd be great for Thanksgiving, but note that it serves 3 to 4. If you're feeding a crowd, scale the recipe up accordingly. Depending on the size of your food processor, you'll likely need to work in batches.
Bring a large pot of salted water to a boil. Add the cauliflower and boil until knife-tender, about 10 minutes. Drain and transfer to a food processor.
Puree the cauliflower with the butter, garlic, mustard, salt, and pepper. Season to taste and garnish with chives, if desired.