1. Preheat oven to 400 degrees F. Combine flour, salt and baking powder in bowl. Using pastry blender or 2 knives, cut in shortening until mixture resembles coarse crumbs. Add 3/4 cup milk, stirring with fork until mixture comes together into pliable, but not sticky dough. Add more milk if needed.
2. Transfer dough to lightly floured surface. Knead until smooth and silky, 5 minutes. Let rest, covered with a damp cloth, for 15 minutes.
3. Shape dough into 12 equal balls. (Keep remaining dough and completed balls covered to prevent drying.) To shape each ball: Hold ball of dough in both hands, thumbs on top and fingers underneath. Working with your fingers, lightly pull and push dough out from center to make a slightly flattened shape like a big mushroom cap, 3 inches across.
4. Lightly coat baking sheet with nonstick cooking spray. Place pieces of dough on baking sheet. Flatten each into a 4-inch circle. Rub a little oil over the tops of semitas. Prick them all over with a fork.
5. Bake in preheated 400 degree F oven until golden, 12 to 15 minutes. Serve at once with butter and fruit preserves. Makes 12 biscuits.