Chocolate Chestnut Bûche de Noël

Name: Chocolate Chestnut Bûche de Noël
Prep time: 30 min
Cook time: 40 min
Total time: 1 h 10 min
Cuisine: French, American
Ingredients: 2 tablespoons sugar; 1 tablespoon water; 1 1/2 tablespoons whiskey; 12 ounces (340 g) peeled and roasted chestnuts (see Tips); 1 1/2 cups (360 ml) water; 3/4 cup (149 g) sugar; 1 teaspoon vanilla; 3/4 cup and 1 tablespoon (125 g) plus extra, low FODMAP, all-purpose gluten-free flour,; 1 teaspoon baking powder, (use gluten-free if following a gluten-free diet); 1/8 teaspoon salt; 1/4 cup (60 ml) lactose-free whole milk; 4 tablespoons unsalted butter, cut into pieces; 1/2 teaspoon (57 g) vanilla extract; 3 large eggs, (at room temperature); 3 large egg yolks, (at room temperature); 1 batch French Whole Egg Buttercream; 7 ounces (200 g) semisweet or bittersweet chocolate, melted and cooled