Heat oven to 200C/180C fan/gas 6. Line each hole of a 12-hole muffin tin with a thin strip of baking parchment across the middle that’s long enough so the ends stick out a centimetre or two – use a dab of butter to stick in place. Roll out two thirds of the pastry on a lightly floured surface and stamp out 12 x 10cm circles (you may need to re-roll trimmings). Press a circle into each hole to line.
Sprinkle 1 tsp of breadcrumbs into the base of each pie. Tip the rest of the crumbs into a mixing bowl. Squeeze in the sausage meat, discarding the skins, along with the bacon, mace, pepper, sage and just a little salt. Get your hands in and mash and squish everything together until the breadcrumbs have just about disappeared. Divide mixture between the holes, packing in firmly and shaping to a dome in the middle.
Roll out the remaining pastry and stamp out 12 x 7cm circles. Brush with a little egg and add a top to each pie, egg-side down to stick, carefully pressing pastry edges together to seal. Brush with more egg (don’t throw away leftovers) and sprinkle with sesame seeds. Bake for 30 mins until golden then carefully remove the pies from the tin, using the parchment ends to help you lift them out. Sit on a parchment lined baking tray, brush all round the sides with more egg and put back in the oven for 8 mins. Cool completely then eat with piccalilli, or your favourite pickle.