Preheat the oven to 475 degrees F. Position an oven rack so it is in the top third of the oven.
Add the flour, baking powder and salt to a medium bowl and whisk to combine. Stir in the olives. Using your fingers or a fork, cut the mascarpone into the flour mixture until it resembles small pebbles in the flour. Add the buttermilk and gently mix until a rough dough is formed. (Do not overmix.) Pour the mixture onto a lightly floured surface and gently gather into a 1-inch-thick square. Using a 2-inch round biscuit cutter, cut as many rounds as your square will allow. Gather the scraps once, reform and cut a few more. (You will have about 12 biscuits.) Place on a small rimmed baking sheet so that the biscuits touch each other. Bake in the top third of the oven until light golden brown and cooked through, 15 to 20 minutes. Serve with orange marmalade and softened salted butter on the side, if using.