Mashed Potatoes with Lemon and Chives

6 tablespoons butter, divided
2 garlic cloves, minced
2 teaspoons grated lemon peel
1/2 cup chopped fresh chives
2 pounds russet potatoes, cut into 1-inch cubes
1/4 cup buttermilk

Melt 3 tablespoons butter in heavy small skillet over medium heat. Add garlic and saut