Billot Log Cake a.k.a. Raspberry Buttercream Log

Sponge Cake
Line the bottom of a 12 x 18 inch jelly roll pan or ridged cookie sheet with parchment paper cut to it’s exact size. Do not grease the pan. Preheat oven to 300 degrees F.

Sift together and set aside:
1 cup flour
1 tsp baking powder
For the meringue base of the batter you will need:
6 eggs separated, room temperature
1/4 tsp cream of tarter
1 cup sugar, separated in 2 portions of 1/2 cup
1 1/2tsp vanilla extract

Beat egg whites and cream of tarter until foamy. Add 1/2 cup sugar gradually until egg whites are stiff.

Beat egg yolks and 1/2 cup sugar until foamy and thickened.

Fold beaten egg yolks into the beaten egg whites along with the vanilla for only a few turns before slowly and gradually folding in the flour and baking powder mixture very gently BY HAND using a rubber spatula until just incorporated into the meringue mixture. I mix in the dry ingredients in 3 equal portions. Do not over mix, you just want the flour to be incorporated; over mixing will deflate the egg whites and result in a tough textured final product.

Spread the batter evenly into the prepared pan and bake for 25 minutes until the center springs back when touched.

Cool in the pan for about 15 minutes. Run a sharp knife around the edge of the pan to release the cake. Cover the top of the cake wit h another sheet of parchment paper and invert onto the counter top. Beginning at the shortest side, loosely roll the cake up, letting it rest with the edge seam on the bottom. Let it cool completely. This technique will allow the cake to be more easily rolled later without cracking when the filling is added.

Vanilla Buttercream Frosting
In the bowl of an electric mixer blend together until the butter is well incorporated:
6 cups icing sugar (powdered sugar)
1 1/2 cups butter

Add:
Approximately 3-4 tbsp milk
2 tsp vanilla extract

Add the milk a little at a time until the frosting is light, fluffy and smooth. I like to beat the frosting for an additional 5 minutes once I get the consistency correct in order to beat in more air and make it lighter and creamier.

To construct the cake:

Unroll the sponge cake and remove the top parchment paper. Spread the frosting evenly over the cake. Sprinkle the surface of the frosting evenly with:
1 1/2 cups fresh raspberries

Starting at a short side of the cake, begin to roll the cake up, removing the bottom parchment paper as you go. The parchment paper is a great help in rolling the cake.

Let the cake rest on a serving plate with the seam side down. Mix together:
3/4 cup raspberry jam or jelly
2 tbsp water

Heat the jelly and water in the microwave or in a small pot on the stove until it is smooth and evenly blended. Brush the heated jelly all over the surface of the cake roll. Finally sprinkle the entire surface of the cake roll with
3/4 cup sweetened dried coconut

Chill the cake in the refrigerator for a couple of hours before serving. I like to make this cake the day before to give time for the raspberries to meld with the sugar in the frosting making it even better.

Notes
Source recipes -Here-