Spray a 7-inch tart pan with removable bottom with cooking spray. If you don't have a tart pan, use a 6 to 7-inch springform pan. Line the bottom of the pan with parchment paper and spray the paper.
- Melt 6 ounces of chopped chocolate and butter in a heavy saucepan over medium low heat. Stir until chocolate and butter are melted and smooth.
- Add sugar and salt and reduce heat to low. Cook while stirring for about one minute, until sugar starts to dissolve.
- Remove pan from heat. Whisk in eggs, one at a time. The mixture will look smooth and glossy.
- Use a mesh hand sieve to sift cocoa into mixture. This prevents lumps. Whisk until the cake batter is smooth.
- Pour batter into prepared pan and bake in preheated oven for about 25 minutes. The center of the cake should be just firm to the touch, but be careful to not overbake the cake or it will be dry.
- Cool in the pan on a wire rack for 15 minutes. Invert the cake on a plate.
- To prepare the glaze, melt 2 ounces of chopped chocolate and 1 1/2 tablespoons of unsalted butter in the same saucepan you used to make the cake. When melted and smooth, remove the pan from heat. Add milk and Agave syrup OR honey and vanilla and stir until smooth and glossy. Let the glaze cool for about 3 minutes before pouring it on the cake.
- Pour all of the glaze in the middle of the cake. Use a silicone or rubber spatula to spread the glaze evenly over the cake, allowing the glaze to evenly run down the sides of the cake.
Reminder: Always make sure your work surfaces, utensils, pans and tools are free of gluten. Always read product labels. Manufacturers can change product formulations without notice. When in doubt, do not buy or use a product before contacting the manufacturer for verification that the product is free of gluten.