Cut potatoes into one-half-inch pieces. Cook in boiling water to cover 15-20 minutes or until tender; drain. Combine potatoes, onions, one-half teaspoon garlic salt and the pepper. Toss gently to combine. Stir together yogurt, buttermilk, blue cheese and remaining one-quarter teaspoon garlic salt. Add to potatoes; toss gently to coat. Cover and chill at least 2 hours. Serves 10.
