Preheat oven to 350 degrees F (180 degrees C).
Add Hazelnuts (1 1/2 cup) to a baking sheet in a single layer. Bake in the center of the oven for about 8 minutes if roasted, or 12 minutes if raw until warmed and lightly golden in color.
Remove nuts from the oven and transfer to a kitchen towel. Using your hands, cover the nuts with the towel and rub to remove and loosen as much skin as possible.
Transfer hazelnuts to a blender or food processor. Blend on low for 1 minute, then scrape the sides. Mix on medium speed for 1 minute and scrape, then blend 1 minute again or until smooth.
Melt the Semi-Sweet Chocolate Chips (1/2 cup) over a double boiler or in a microwave at 30-second increments until melted. Transfer melted chocolate, Unsweetened Cocoa Powder (2 teaspoon), Vanilla Extract (1/2 teaspoon), and Kosher Salt (1/8 teaspoon) to the blender.
Blend for 1 minute on medium spend. Add Pure Maple Syrup (1 teaspoon) and blend another 10 seconds. Taste and add more maple syrup if desired. Transfer to a container with a lid and refrigerate until ready to fill the cakes.
Preheat the oven to 450 degrees F (230 degrees C).
Melt Unsalted Butter (1 tablespoon) in a microwave safe dish for 30 seconds. Brush melted butter on the inside of four 8 ounce ramekins. Lightly coat with Gluten-Free All-Purpose Flour (2 tablespoon), tap out the excess flour.
Set the ramekins on a baking sheet. In a double boiler, over simmering Water (to taste), melt Unsalted Butter (8 tablespoon) with Bittersweet Chocolate (6 ounce), remove from heat and whisk together to combine.
In a medium bowl, whisk the Large Egg (2), Granulated Sugar (1/4 cup), and Kosher Salt (1 pinch), at high speed until thickened and pale, about 3 minutes.
Quickly fold chocolate into the egg mixture. Fold in the Gluten-Free All-Purpose Flour (2 tablespoon), until combined. Evenly divide the batter about half full into the 4 prepared ramekins. Add 1 tablespoon of the nutella mixture into the center of each ramekin.
Bake on a sheet tray for 9 minutes, or until the sides of the cakes are firm, the tops are just slightly cracked, but the centers are soft and slightly jiggly.
Let the cakes cool in the ramekins for 1 minute. Run a knife or small spatula along the sides of the ramekins a few times to release the cake. Cover each ramekin with an inverted dessert plate. Carefully turn each one over, let stand for 10 seconds and then unmold.
Use the spatula or knife to lift the corner of the ramekin and a gloved hand to lift and unmold the cake. Add desired toppings.
Serve immediately and enjoy!