Preheat the oven to 400 degrees F. Line a baking sheet with parchment paper.
Throw the flour, cocoa powder and baking soda into a bowl and whisk until combined. Combine the raw sugar, vanilla extract and egg in a stand mixer and mix on high speed until smooth and thick, 3 minutes. Turn the speed down to low and slowly stream in the melted butter. Add in the dry ingredients and mix on low until fully incorporated.
Drop heaping tablespoons of dough 2 to 3 inches apart on the baking sheet, and bake 7 minutes. Cool on the baking sheets about 3 minutes, and then sprinkle with the Honeycomb while the cookies are still soft. Press the Honeycomb into the cookies and sprinkle with a pinch of fleur de sel.
Line a baking sheet with lightly buttered parchment paper.
Stir together the sugar and honey in a medium saucepan over medium heat until the sugar is dissolved. Cook the sugar, monitoring with a candy thermometer, until it reaches 300 degrees F (hard crack stage), about 10 minutes.
Whisk in the baking soda and vanilla. As soon as the mixture begins to puff, about 30 seconds, pour it out in a flat layer onto the baking sheet. Let harden 30 minutes.