Preheat oven to 425 degrees F. Line 2 baking sheets with parchment paper and set aside.

In a medium saucepan bring the water, butter, salt and sugar to a rapid simmer. Remove from heat and immediately stir in the flour with a wooden spoon. Keep stirring rapidly until the mixture comes together for about 30 to 60 seconds. Return to the heat and cook, constantly stirring rapidly, for about 30 seconds. Transfer the mixture to a stand mixer, fitted with the paddle attachment, and stir on medium. Slowly add the eggs, one at a time, mixing well after each addition. Scrape down the sides and bottom of the bowl and mix once more. The batter should be thick, but fall slowly away from the paddle. Transfer to a large pastry bag fitted with a large star tip.

Pipe out the eclairs onto the prepared baking pans, to about 2 inch think logs. Make sure to leave about 2 inches of space apart. Brush the surface of each eclair with the egg wash and bake for 15 minutes. Reduce the heat to 375 degrees F and continue to bake until puffed and golden brown, about 25 minutes more. Let the eclairs cool completely on the baking sheets.

Pour the melted butter into a shallow baking dish. In a separate shallow dish, combine the sugar and ground cinnamon until evenly combined. Dip each cooled eclair into the melted butter, turning over to coat both sides, and then roll around in cinnamon sugar. Return to the baking sheet and continue coating the rest.

Pour the heavy cream in a small saucepan and set over medium-low heat, bringing to a low simmer. Pour the chocolate into a medium bowl, along with the butter, cinnamon, cayenne and salt. Once the cream has heated through, pour over the chocolate and let sit for 10 minutes before stirring until smooth and completely melted through. Allow the ganache to cool completely. You can place in the fridge to speed the process up. Transfer the firmed ganache into a large mixing bowl and beat on high until light and fluffy. Transfer the whipped ganache into a piping bag, fitted with a star tip.

Using a serrated knife, cut each of the cinnamon sugar eclairs in half, lengthwise. Then fill each with the whipped ganache and sandwich together. Serve immediately or store in the fridge until ready to eat. Enjoy!