Preheat oven to 425°.
Combine first 9 ingredients in a large bowl; toss well. Divide potato mixture into 8 (1/2-cup) portions, shaping each into a 1/2-inch-thick patty.
Melt 4 teaspoons butter in a large nonstick skillet over medium-high heat. Add 4 patties to pan; cook 5 minutes on each side or until golden. Place on a baking sheet. Repeat procedure with remaining 3 1/2 teaspoons butter and remaining 4 patties.
Bake patties at 425° for 8 minutes or until thoroughly heated. Serve with fat-free sour cream, if desired.