Preheat oven to 375° F. Soak raisins in hot water for 5 minutes and drain off excess water. Set aside. Stir together flour, sugar, baking powder and salt. Cut in butter with fingers until only a few visible pieces of butter remain. Stir in 1 cup milk, just until dough comes together. Add raisins.
Turn dough out onto a lightly floured surface. Divide dough in two and shape into 2 rounds, flattening to about 3/4–inch thick with your hands. Cut each round into 8 wedges. Place biscuits on a parchment-lined baking sheet and brush with remaining 2 Tbsp milk. Bake for 15 to 18 minutes, until evenly browned.