Mix together the chestnut puree, onion, garlic, lemon juice, soy sauce, breadcrumbs and chilli powder. Leave mixture for a few minutes for the breadcrumbs to thicken it then add a few more if necessary to make a soft mixture which you can roll into sausages. Set the oven to 190 degrees centigrade or gas Mark 5. On a lightly floured board roll out the pastry quite thinly, then cut across into long strips, about 2 inches wide. Roll pieces of the chestnut mixture into sausages about the width of slim little fingers and the length of the pastry strips. Lay the mixture on top of the pastry strips. Dampen the edges with cold water then roll them around the chestnut mixture pressing the edges together. Prick the pastry with a fork and cut into 1 inch lengths and place, seam down, onto a pastry sheet. Bake for 10 mins until golden brown.