Preheat oven to 350.Cut four pieces of foil or nonstick parchment paper large enough to wrap each Clementine and put one Clementine on each piece. Mix butter with powdered sugar, pistachios, and liqueur. Spoon flavored butter over top of each Clementine, then enclose foil or paper, twisting edges to secure. Place on baking sheet and cook in preheated oven to 10 minutes, til hot.
Preheat waffle machine. Sift flour, baking powder and baking soda into mixing bowl. Add fruit and zest, and sugar. Mix butter, egg, milk and liqueur together in another bowl, then gradually beat into dry ingredients til smooth.
Spoon batter into waffle machine close lid, and cook til browned and well risen.
Cut waffles in half land transfer to serving plates. Unwrap the Clementine's and put one on top of each waffle. Add a spoonful of plain yogurt (or sour cream) then drizzle with the buttery juices. Dust with a little sifted powdered sugar and serve at once. Makes 4