Finely dice the shallot, sage leaves and garlic.
Heat the butter in a frying pan and add the shallot. Once it has softened and gone translucent, add the garlic and sage leaves for another minute before removing to a bowl and place in the freezer for five minutes to chill it down quickly.
Now mix it with your pork mince and season with salt and pepper. You can mix it with utensils but really it's easiest using your hands. Cover the bowl in cling film and chill for 30 minutes to let the flavours combine.
Preheat the oven to 400 F / 200 C and grease an oven tray or line it with baking paper.
Cut the puff pastry into long strips that are 4 inches or 10 centimetres wide
Take the pork mince with sage and garlic out of the fridge and form a sausage long ways down the middle of the pastry running from end to end. Be sure to leave a small gap on either long side.
Crack an egg into a cup or glass, mix the yolk and white together and brush it along the pastry on either side of the pork mince.
Take another layer of puff pastry and place it on top, forming it around the pork mince.
Fold the edge of the bottom layer over the edge of the top layer on the long side, and then crimp the two layers together by pressing a fork into them. This, and the egg wash will keep the two layers of puff pastry together whilst baking.
Make the crunchy topping by mixing the dried minced garlic, sesame seeds, black onion or nigella seeds and poppy seeds together in a small bowl.
Brush another layer of egg wash over the top of the sausage roll and sprinkle the seed mix over the top.
Now cut the sausage roll into small pieces using a sharp knife that are around 2 inches or 5 centimetres long.
Place them on the oven tray and bake in the oven for 15 minutes, and check to see how they are doing. They should be toffee coloured golden brown on top. Depending on your oven they might need up to another 5 minutes.