Family Style Food

Make the cake
1 Heat the oven to 350 (175 C) degrees with the rack placed in the center. Grease a 9 x 13-inch pan with the butter and sprinkle with the flour. Rotate the pan to coat and tap out the excess flour.
2 Whisk together the flour, baking powder and salt in a bowl.
3 In a heavy-duty mixer fitted with the paddle attachment, beat the eggs on medium-high speed just to break them up. Add the sugar and beat 1 or 2 minutes, until thickened and smooth. Pour in the oil in a slow steady stream until the mixture looks emulsified. Add the mascarpone, milk, lemon zest, vanilla and lemon extracts and mix until smooth. 
4 Stir the flour mixture into the batter in two additions, mixing just until the flour is incorporated.
5 Scrape the batter into the prepared pan. Bake 35 - 40 minutes, or until a toothpick inserted in the center comes out clean. Cool the cake completely on a wire rack.
Icing
1 Combine the sugar and lemon juice in a bowl. Stir in the mascarpone until smooth. Add more sugar if you want a thicker icing, or more lemon juice to thin.
2 Spread the icing on the cooled cake (this is easier if you invert the cake onto a baking sheet, then flip right side up onto another baking sheet). Arrange the blueberries on top and sprinkle with the mint and lemon zest.