Preheat the oven to 375 degrees F. Line a baking sheet with parchment paper and set aside.
In a medium saucepan over medium-high heat, bring the milk, butter, and the 1/4 teaspoon salt to a boil. When the butter has melted, remove from the heat and add the flour all at once. Using a wooden spoon, beat the mixture vigorously until it forms a ball. Return to medium heat and continue stirring for 1 minute, or until the mixture dries. Remove the mixture from the saucepan
and spoon it into a food processor
. Let cool for 5 minutes. After it has cooled slightly, process for a few seconds. Add the eggs and cayenne and process for another 15 seconds, or until it is well combined. Transfer the mixture to a mixing bowl and let cool for 10 minutes. Stir in the cheese and bacon until they are just incorporated.
Scoop out 1 heaping tablespoon of dough and push it off the spoon onto a prepared baking sheet with a second spoon (or use your finger). Repeat with the remaining dough
, spacing the mounds 2 inches apart. Sprinkle the tops of the puffers with fleur de sel
. Bake for 30 minutes, or until browned and crisp. Serve warm.