Melt butter in a medium frying pan over high heat. Add pineapple and cook until caramelized slightly, about 5 minutes. Add amaretto and cook until it resembles a syrup. Stir in basil. Scoop about 1/2 cup frozen yogurt into each of 4 serving dishes, then spoon warm pineapple mixture on top.
Note: Nutritional analysis is per serving.