2 tbsp. butter
2 tbsp. dark brown sugar
2 c. leftover cooked sweet potatoes or yams, cut into chunks
1/2 tsp. salt
1/4-1/2 c. heavy cream

Melt butter over medium heat. Add brown sugar and sizzle for 1 to 2 minutes. Add potatoes or yams and salt. Heat thoroughly, mashing potatoes or yams with back of spoon. Stir in enough of the cream to make moderately stiff puree. Place mixture in food processor or blender. Whirl until puree. Scrape puree into a pastry bag fitted with 1/2" star tip. Pipe equal amounts onto 4 dinner plates.