1Preheat oven to 375°F.
2In a large bowl or the bowl of a food processor, combine the flours, sugar, baking powder and salt. Blend using a pastry cutter or fork, or pulse the food processor until the mixture is combined but there are still bits of butter no bigger than a pea.
3If you’re using a food processor, dump the mixture out into a bowl. Add the buttermilk, cream or milk, and stir just until the dough comes together. Divide it in half, and on a floured surface roll each piece into a 10" square. Spread the jam in a strip down the middle third, and fold each half over it, overlapping like a letter. If you like, brush the tops with a little extra milk and sprinkle with sugar.
4Transfer to a baking sheet and bake for 25-30 minutes, until golden. To serve, cut into thick slices, or triangle-shaped wedges by cutting at alternating angles.