Cauliflower Shepherds Pie (Low Carb)

1 large head Cauliflower
3 tablespoons cream cheese
2 tablespoons butter
2-3 tablespoons milk
1 teaspoon chopped garlic
1 1/2 lb. lean ground beef, cooked and drained
1 teaspoon dried thyme
1 (4 oz) can mushrooms, drained
2 cups cheddar cheese, shredded
1 tablespoon chopped chives, optional

Preheat oven to 350 degrees. 
Chop cauliflower and steam until very tender.
Put in a food processor along with cream cheese, butter, milk and garlic.
Mix well and add season to taste. 
Spray a 9x13 baking dish with a non-stick cooking spray and sprinkle with 1 cup of cheese
and top with ½ of the cauliflower puree. 
Next pour on the hamburger meat and mushrooms then the rest of the cauliflower puree. 
Top with the rest of the cheddar cheese and chives.
Bake for about 30 minutes or until heated through.