As the onions cook, stir together the sour cream, yogurt, onion powder, salt and dried sage. Add the onion powder to taste. I pretty much used the full 4 teaspoons because the onion powder is what gives this that sweet French flavor. Add a bit at a time until it tastes the way you want it. Set aside until the caramelized onions and garlic have cooled to room temperature. Stir in the onions, adding lemon juice at this time, to taste, as well. Add chives, reserving 1 tablespoon to garnish on top, if desired.