Using a wooden or heatproof plastic spatula, cut the pancake in the skillet into 2-inch squares. Dot with the remaining 2 1/2 tablespoons of butter, sprinkle with the 1/3 cup of confectioners' sugar and top with the peaches. Cook, tossing, until the pancake is caramelized, about 5 minutes. Add the blackberries and toss until they are heated through, about 1 minute. Transfer the <em>kaiserschmarrn</em> to a platter, sprinkle with confectioners' sugar and serve.