Yule Log with Chocolate and Chestnut Buttercream

Ingredients:

Cake: 100 grams of all purpose flour
Cake: 30 grams of corn starch
Cake: 130 grams of sugar
Cake: 4 large eggs
Cake: 1 teaspoon of vanilla extract
Chestnut Buttercream: 500 grams of chestnut cream
Chestnut Buttercream: 250 grams of butter (soften)
Chocolate Buttercream: 100 grams of dark chocolate + 1/3 portion of the chestnut buttercream
Syrup: 100 grams sugar
Syrup: 2/3 cup of water (15 cl)
Syrup: 1 tablespoon of orange blossom water