Blackberry + Champagne Layer Cake

Even thought the seasons may technically begin on a date determined by the relation of Earth to the sun, they do not always begin at the same time in spirit. Specifically, last week's heatwave was a teasing little snippet of a summer that never came. In the spirit of summer that hadnt the chance to live, and the newborn autumn. Blackberries are a wonderful transitional fruit - berries are always somewhat summer-like, but their dark color and deliciously mellow flavor makes them feel right in the colder weather. Yet, blackberries are fickle - you never know what you'll get - sweet or tart.
I usually eat mine with a honey mascarpone whipped cream. It is a very simple dessert, lovely and fresh, and one of my favorites. This year, I have not been able to find good blackberries. And I was in the mood for making a classic, old-fashioned cake. I wanted to use blackberry flavor in that cake - and to use dark blackberries in contrast to some snowy white frosting. Since the cake was for a party, I decided to use a celebratory drink to flavor a classic white buttermilk cake. And thus, a party cake of champagne and blackberries was born. Next time, I don't want to wait for a party to make this cake - it is lovely enough to make for yourself to enjoy with a cup of tea or maybe even a glass of champagne.

Blackberry Champagne Layer Cake
For cake:
2 cups cake flour
2 tsp baking powder
1 tsp each baking soda, salt
10 tbsp butter (1 stick+ 2 tbsp), softened
1 1/4 cup sugar
1 cup buttermilk
4 large egg whites
1/4 cup champagne/sparkling wine
+ 2/3 cup blackberry jam for spreading between layers
Prepare two 9 X 1.5 inch or 8 X 2 inch round cake pan by greasing them with butter and placing a circular cutout of parchment to cover the bottom. Preheat oven to 350°F.
Mix together sifted cake flour, baking powder, baking soda and salt in a medium bowl, set aside. In a large bowl, whip butter until it is noticeably lighter. Add sugar, beat until the mixture is light and fluffy. Beat the buttermilk and egg whites. Add the dry ingredients to the butter-buttermilk mixture and beat until more fluffy. Gently stir in champagne - do not overmix as you want the champagne to retain the bubbles.
Divide evenly to prepared cake pans. Bake for 25-30 minutes, or until a cake tester inserted into the center comes out clean.

For mascarpone whipped cream
1 1/2 cup whipping/heavy cream
1/2 cup (approximately 6 oz) mascarpone
1/4 cup powdered sugar
optional: 1 tbsp honey, 1 tsp vanilla extract (I used honey in mine)
Whip together all of the ingredients in a large (preferably cooled metal) bowl, until soft peaks form. If you need to take a break while whipping, place bowl in the freezer during this time - this will help the cream set faster.
To Assemble
Allow cakes to cool for at least 10 minutes remove removing from pan. After removing, allow cakes to cool completely - at least another 15 more minutes. In the meantime, heat the blackberry jam to make it more spreadable. Then, level cakes if necessary. Brush off all crumbs. Beginning with the cake that is to be the bottom layer, spread the 2/3 cup of blackberry jam onto the cake, leaving the 1/4 inch on the edge of the cake clean. Spread a layer of mascarpone whipped cream over the blackberry layer. Carefully place the top layer of cake onto this. Frost the assembled cake with mascarpone whipped cream (I did this by spreading a thin layer of whipped cream over the cake, chilling it to set it, and then finishing with a thicker layer).