Cut the venison and pork fat into 1 to 2-inch pieces.
In a large bowl, combine the meat and fat chunks with the seasoning mix and milk powder (if using). Toss until evenly combined. Place in the freezer and chill until nearly frozen.
Grind once through a coarse plate (8–10 mm), then once more through a medium plate (4.5–6 mm). Keep meat cold between grinds by grinding the sausage into a bowl that is set over a larger bowl filled with ice.
Using either your hands or a stand mixer fitted with a paddle attachment, start mixing the sausage. Slowly add the ice-cold water and while mixing until it is fully incorporated and the sausage is tacky to the touch. This will take around 1 minute with the stand mixer and around 3 minutes by hand.
Cook a small patty to test seasoning. Adjust salt or spices if needed.
Stuff into natural casings for links, or portion into patties or bulk packs.
Store fresh sausage in the refrigerator for up to 3 days, or vacuum seal and freeze for longer storage.