How to Make It
Arrange potatoes in a microwave-safe dish; cover tightly with plastic wrap. Cut a 1/2-inch slit in plastic. Microwave at HIGH 8 minutes or until tender; transfer to a bowl. Microwave buttermilk in a microwave-safe cup 30 seconds; pour buttermilk and 2 tablespoons olive oil over potatoes. Mash until mostly smooth.
While potatoes cook, heat 1 1/2 teaspoons olive oil in a large skillet over medium heat. Add minced fresh garlic to pan; cook 1 minute or until fragrant. Add spinach to pan; cook 1 minute or until spinach wilts, stirring constantly. Stir spinach mixture, salt, and pepper into potatoes. Serve potatoes immediately.