These cheesy puffs are a French classic. It's impossible to stop at one… but then who's counting?
Preheat the oven to 145°C (convection). Bring the water to boil in a pan with the tsp table salt and 1/2 cup softened butter in pieces. Remove from the heat and incorporate the 11/3 cups sieved flour. Mix with a spatula to a smooth dough. Return to the heat in a saucepan for 3 minutes to dry the pastry, stirring vigorously.
Transfer the dough to a mixing bowl. Incorporate the 5 eggs, one at a time, stirring. To finish, add the shredded Gruyère. Heat the remaining 3 tbsp butter in one saucepan and warm the milk in another. Once the butter is foamy, add the 1/3 cup flour and mix with a wooden spoon. Then pour in the warm milk, stirring continuously. Continue until the mixture begins to boil. Then add the tsp of salt, the 1/2 tsp of ground pepper and the shredded Comté. Set aside.
Place the choux dough in a pastry bag with a plain 10 mm tip. Pipe the puffs onto a baking sheet lined with parchment. Beat the remaining egg and brush the puffs with it. Sprinkle on the toasted sesame seeds and a few grinds of ground pepper. Bake for 25 minutes, until the choux are puffed up and golden brown.
Once they are cooked, transfer the Comté sauce to a pastry bag with a small plain tip and fill them from underneath. Serve warm.