Preheat the oven to 170°C and line two baking sheets with parchment paper.
Heat a small frying pan over medium heat.
Melt the butter in a medium pan with the milk over low heat.
Fry the pancetta in a drizzle of oil for four minutes until golden.
Bring the milk and butter mixture to a boil.
Mix grated parmesan, flour, chilli powder, and salt in a bowl.
Stir the flour mixture into the boiling milk and beat until it leaves the pan sides.
Drain the pancetta on kitchen towels and chop it finely.
Beat the eggs into the cooled flour mixture one at a time, then stir in the pancetta.
Spoon or pipe 3cm blobs onto the sheets and flatten any peaks with a wet finger.
Bake for 25 minutes until the puffs are crisp and golden.