My Kind of Chocolate Birthday Cake

INGREDIENTS

• 2 tablespoons sugar
• 1 tablespoon light corn syrup
• 1 1/2 cups chilled heavy whipping cream, divided
• 1 tablespoon all purpose flour
• 2 tablespoons unsalted butter
• 1/2 teaspoon coarse kosher salt
• Additional toasted husked hazelnuts
• 1/2 cup heavy whipping cream
• 2 large eggs
• 4 ounces bittersweet or semisweet chocolate, chopped
• 1/2 cup hazelnuts, toasted, husked, chopped
• Large chocolate shards or curls (from 1- to 2-inch-thick 8-ounce piece bittersweet or semisweet chocolate)
• 4 ounces bittersweet or semisweet chocolate
• 1/2 teaspoon grated orange peel
• 5 ounces bittersweet or semisweet chocolate, chopped
• Candied orange peel strips
• chopped 1 tablespoon unsalted butter, room temperature
• 3 ounces high-quality milk chocolate (such as Lindt or Perugina), chopped
• 5 tablespoons unsalted butter, room temperature
• 1/3 cup (packed) dark brown sugar