Cooking Down Apples

When adding apples to sausage filling, you must cook them down completely until soft, with all water evaporated. Raw or undercooked apple pieces release moisture during baking, which creates soggy pastry and causes the filling to steam rather than properly brown. 

The recipe specifies cooking diced apples with just 3 tablespoons of water until they become completely mushy and all liquid disappears. This concentrates the apple flavor while eliminating excess moisture that would compromise puff pastry's crisp, flaky layers. The cooked apple puree binds into the sausage meat seamlessly, adding subtle sweetness and moisture to the filling without making it wet. 

Always let cooked apples cool before mixing into meat to prevent warming the fat in the sausage, which should stay cold for best texture. This same moisture-removal technique applies to any fruit or vegetable additions to pastry-wrapped fillings.