Foryoueats: Pepper Jack Mashed Potatoes

1 1/2 sticks salted butter, plus more for the baking dish

5 lb. pounds russet potatoes, peeled and cut into 2-inch chunks

6 garlic cloves, crushed and peeled

1 1/2 tsp. kosher salt, plus more to taste

4 oz. cream cheese, at room temperature

3/4 c. half-and-half

1/2 tsp. chili powder, plus more for sprinkling

1/2 tsp. cayenne pepper, plus more to taste

8 oz. pepper jack cheese, shredded (about 2 cups)

Thinly sliced scallions, for garnish

Pepper Jack Mashed Potatoes