To Prepare Candied Clementines and Syrup
- In a saucepan, bring water, sugar, honey, and rosemary to a boil, stirring until sugar dissolves. Add clementine slices and reduce heat to a simmer, turning slices until tender and syrup is reduced, about 40 minutes.
- Strain clementine slices, reserving syrup to use on cake.
- On a baking sheet lined with parchment paper, arrange slices in a single layer. Cool completely before using to decorate.
To Prepare Cake
- With a rack set at position “3,” select Gourmet Mode and choose Baked Goods, Cake, Sheet, and then One Rack.
- Grease a 10-inch cake pan with a knob of butter and line the bottom with parchment paper.
- Sift together flours, baking powder, and salt. In another bowl, whisk melted butter with olive oil.
- Place eggs, sugar, and clementine zest in the bowl of a stand mixer. Mix on high until pale and thickened, about 3 minutes. Lower mixer speed and alternate adding the dry and wet ingredients, starting and ending with the dry.
- Once mixed, pour batter into prepared cake pan. Bake for 40–45 minutes, until golden brown.
- Once baked, poke holes all over the top of the cake with a skewer.
- Pour 1 cup of the reserved clementine syrup on top of cake. Let cool to room temperature before transferring to a cake stand.
To Prepare Frosting
- Place mascarpone, confectioner’s sugar, heavy whipping cream, and clementine zest in a food processor and pulse until smooth.
- Dollop frosting in the center of the cake, spreading evenly toward the edges. Sprinkle with chopped pistachios. Top with candied clementine slices and rosemary sprigs.