Toss berries with the sugar - cover and refrigerate 3 hours.
Preheat oven to 400 degrees. Combine the flour, 2 tablespoons sugar, poppy seeds, cream of tartar, baking soda and salt in a food processor. Add butter and pulse until mixture resembles coarse meal. Add half and half, mix just until moist clumps form. Turn dough out onto floured surface, knead 2 - 3 times to smooth, roll out to 1/2 inch thick. Cut using a 3 inch round cutter. Transfer to a baking sheet lined with parchment. Bake until golden brown, about 12 minutes. Cool on rack. Using a serrated knife, cut biscuits horizontally in half. Place lower halves cut side up on plates. Top with berries and whipped cream, if desired.