Heat oven to 375°F. Cut each potato crosswise into 1/8-inch slices, cutting only three-fourths of the way through to bottom of potato. Place cut sides up on ungreased 15x10-inch pan. Arrange garlic slices between potato slices. Sprinkle with salt and pepper; brush lightly with some of the pesto.
Bake 45 to 55 minutes or until potatoes are tender. Brush with additional pesto before serving. If desired, garnish with grated Parmesan cheese and parsley.