Melt the butter in a skillet. Add the bacon and fry until crispy. Remove from pan and chop.
In a bowl , mix with parsley, a pinch of pepper and mustard to taste. Mix the bacon with choux paste and form balls.
Heat oil to 180 or 190 ° C until a dice of dry bread is toasted in 30 seconds. Fry donuts in batches for a few minutes until they rise and remain round. Let drain on paper towels and serve hot .