Finely shred potatoes and onion, if using. Place in sieve; press to remove excess moisture.

In bowl, whisk together egg whites, flour, salt, and baking powder until smooth. Stir in potato mixture.

In large nonstick skillet, heat 2 teaspoons oil over medium-high heat. When drop of water spatters on skillet, spoon potato mixture, about 2 tablespoons at a time onto skillet; form into 3-inch pancakes.

Cook for 4 minutes on each side or until golden brown. Transfer to ovenproof plate. Keep warm in oven while remaining batch or batches cook, adding remaining oil as required.

Serve with sour cream or yogurt.

This recipe yields 6 servings. Serving size: 2 latkes.

Exchanges Per Serving: 1 Fat, 1/2 Starch.

Nutrition Facts: Calories 90; Total Fat 4g; Saturated Fat 0g; Cholesterol 6mg; Sodium 425mg; Potassium 229mg; Carbohydrate 10g; Protein 2g.