Finely chop the shiso and spring onions, grind the black pepper and juniper. Mix all the ingredients into a large bowl and using your hands mix thoroughly. Beating and punching the mixture with your hand until the mixture is sticky and paste like. The mixing part is very important to get a soft texture after cooking.
Form the mix into 16 even size balls and chill in the fridge. Approx 40g each.
Lightly wet your hand with sesame oil to stop the mixture sticking and form each ball around a skewer. Making an oval shape around the skewer around 1 cm from the tip and 6cm in length.
Finally chop the garlic, ginger and spring onions. In a medium size pot place the chopped mixture with the juniper berries in with the mirin and sake.
Reduce this over a medium heat until almost evaporated. Turn the heat down and add the two types of sugar, stir until this is dissolved. Then add the soy sauce. Simmer on a low heat for 5 mins. Allow to cool all together then strain through a fine sieve, pushing every last drop of liquid through. Store this in a thin, high sided container that the skewers can sit in.