Glaceed fruit, such as Glaceed Figs (http://www.marthastewart.com/255998/glaceed-figs), or apricots and clementines, for decorating
Make the cakes: Preheat oven to 350 degrees. Butter two 8-by-2-inch round cake pans, then line with parchment. Butter parchment, and dust pans with flour, tapping out excess. Whisk together flour, baking powder, and salt in a medium bowl.
Cream butter and 1 cup granulated sugar with a mixer until light and fluffy. Add vanilla seeds.
With mixer on low speed, add flour mixture, alternating with milk, starting and ending with dry ingredients. (Scrape down sides as needed.)
Whisk whites with a mixer on high speed until soft peaks form. Slowly add remaining 3/4 cup granulated sugar, beating until stiff, glossy peaks form. (Do not overbeat.) Whisk 1/3 of the whites into batter, then carefully fold in remaining whites.
Divide batter between pans. Bake until testers inserted in centers come out clean, 35 to 40 minutes. Let cool in pans on wire racks for 15 minutes. Run a knife around edges of pans to loosen cakes. Invert cakes onto wire racks, and let cool.
Make the brandy simple syrup: Bring granulated sugar and water to a boil in a small saucepan, stirring until sugar dissolves. Remove from heat, and stir in brandy. Let cool. (Syrup can be refrigerated for up to 1 week.)
Make the mincemeat: Combine everything except the Cognac in a medium saucepan over medium heat. Bring to a simmer, stirring often, then cover and reduce heat to low. Cook, stirring occasionally, until dried fruits are soft and beginning to break down, about 30 minutes. Stir in Cognac, and cook for 5 minutes more. Let cool.
To assemble the cake: Whisk 1 1/2 cups cream until soft peaks form. Trim tops of cakes to create flat surfaces. Slice each cake in half horizontally. Place 1 layer on parchment, cut side up, and brush with simple syrup. Spread with 1 cup cooled mincemeat and 1 cup whipped cream. Top with another cake layer, cut side up. Brush with syrup, and top again with mincemeat, then whipped cream. Repeat layering, ending with a cake layer, flat side up. Refrigerate for at least 2 hours (or overnight).
Whisk remaining 2 cups cream until soft peaks form. Frost cake with whipped cream. Decorate with glaceed fruit, and serve immediately.