Special equipment: Pastry bag fitted with a small star piping tip
For the frosting: In a medium bowl, using an electric hand mixer, beat the mascarpone and vanilla until smooth. Gradually beat in the powdered sugar until the mixture is thick and smooth. Using a spatula, transfer the frosting to a piping bag fitted with a small star piping tip.
For the Santas: Using a paring knife, cut off the leaf-end of each strawberry to make a flat surface. Cut a 1/2- to 3/4-inch piece from the pointed end of each strawberry and reserve as the hats.
Place the strawberries, wide-side down, on a work surface. Pipe a 3/4-inch-high swirl of frosting on each strawberry. Place the hats on top and pipe a small ball of frosting on top of the hats. Press two chocolate chips, pointed-sides inward, into the swirl of frosting to make eyes.