Cake
Unsalted butter, for pans
1 cup all-purpose flour
1/4 cup cornstarch
6 large whole eggs, plus 4 large egg yolks, all at room temperature
1 cup granulated sugar
1/4 teaspoon salt
1 teaspoon pure vanilla extract
3/4 cup vegetable oil
Topping
1 quart (4 cups) heavy cream
1/2 cup powdered sugar
1 teaspoon pure vanilla extract
1 vanilla bean, split lengthwise (optional)
1 pint small strawberries, hulled
1/2 pint blackberries
1/2 pint raspberries
1/2 pint golden raspberries
1/2 pint blueberries
fresh mint leaves for garnish
1. Preheat the oven to 350 degrees. Butter two 9 by 2 inch round cake pans, set aside.
2. In a large bowl sift together flour and cornstarch, set aside.
3. In the bowl of an electric mixer with the whisk attached combine the whole eggs, egg yolks, granulated sugar, salt and vanilla extract. Beat on high speed until thick and pale, it should hold a ribbon like trail on the surface when the whisk is raised. This should take about 5 minutes, scrape down the sides of the bowl as needed.
4. Add flour mixture to the egg mixture. With mixer on low speed beat until just combined. Add oil in a steady stream, mixing until just combined. Remove bowl from mixer. Using the whisk fold the mixture several times.
5. Divide the batter between pans and smooth tops. Bake, rotating pans halfway through, until the cakes are springy to the touch and a cake tester inserted in the center comes out clean, about 30 minutes.
6. Immediately invert cakes onto a wire rack. Then re-invert cakes and let them cool completely with the top sides up.
7. In the bowl of an electric mixer with the whisk attached combine heavy cream, powdered sugar and vanilla extract. Scrape in the vanilla seeds from the vanilla bean if you are using it. Starting on low speed and gradually increasing to medium-high, whip until stiff peaks form, about 2 minutes.
8. Using a serrated knife, trim the tops of the cakes to make level. Slice each cake in half horizontally into two layers. Place one of the bottom layers on a serving plate. Spread a quarter of the whipped cream over the layer, arrange a quarter of the mixed berries on top. Repeat with remaining cake layers, cream and berries. Garnish top with mint leaves (optional). Serve immediately.