In large skillet, melt butter. Add ham and green onion. Cook over medium-high heat, stirring constantly until onion is tender. In bowl, beat together eggs, sour cream, Parmesan cheese, salt and pepper. Add to ham mixture. Cook, without stirring, until mixture begins to set on bottom. Draw a spatula across bottom of pan to form large curds. Continue cooking until eggs are thickened but still moist; do not stir constantly. Serve immediately over toasted English muffin halves. Serves 6.