Preheat oven to 180ºC/350F.

Grease and flour two 8" cake tins and line the base with parchment. Or you could use 3 small cake tins.

Sift the flour, baking powder, and salt until well combined.

Cream the butter and sugar on med-high until pale and fluffy This should take at least 3-4 minutes. Reduce speed and add the room temperature eggs one at a time fully incorporating after each addition and then add the vanilla.

Add the flour and buttermilk, alternating, beginning and ending with flour and fully incorporating after each addition.

Bake for 30-35 minutes or until a skewer inserted into the centre of the cake comes out clean.

Allow to cool for 10 minutes before turning out onto a wire rack

Put sifted icing sugar and butter in an electric mixer fitted with a paddle attachment. Start mixing on the lowest speed. Increase speed to medium and beat until fluffy, scraping down the sides occasionally, about 3 minutes.

Add mascarpone cheese and vanilla extract, mixing on medium-low until creamy. Do not over mix frosting at this point, or the butter and mascarpone could separate.