In small saucepan, bring juniper berries and 2 cups water to boil. - Reduce heat to low, cover and simmer for 10 minutes until berries rehydrated. Drain and let cool, then mince.
Cut venison and pork into pieces that will fit in grinder. Grind on coarse into a cold bowl.
Add juniper berries, mushrooms, garlic, mustard seeds, sage, rosemary, salt, pepper, to the meat. Using mixer stir until combined, then add 1/4c juniper water and stir for 90s until it holds together.