Chill the meat and fat until they is almost frozen by putting it in the freezer for an hour or so. While everything's cooling, toast the cloves and allspice in a dry pan until they smell good, about a minute or two. Grind them to a powder and mix with the salt, mace and ginger.
Take out some hog casings — you’ll need about 3 to 4 standard lengths, about 10 feet — and set in a bowl of very warm water. Mix the eggs, cream, chives, sage and lemon zest in a bowl and put in the fridge.
Mix the salt and spices into the meat and fat with your hands. If you have time, let this rest in the fridge for about an hour or even overnight. But if you are pressed for time, you can go right to grinding.
Grind through your meat grinder (you can use a food processor in a pinch, but you will not get a fine texture) using the fine die. If your room is warmer than 68°F, set the bowl for the ground meat into another bowl of ice to keep it cold. Put the mixture back in the freezer while you clean up. When the mixture is anywhere from 27°F to 33°F, you are ready to mix.
Add the egg-cream mixture to the meat, then mix thoroughly with your (very clean) hands. When I say "thoroughly," I mean for 3 to 4 minutes. It's really important to do this to get the sausage to bind properly. (Tip: If your hands aren't achingly cold while you are doing this, you need to stop and chill the mixture some more.) Once it is mixed well, put it back in the fridge while you clean up again.
Stuff the sausage into the casings. Twist off short, 5-inch links by pinching the sausage down and twisting it, first in one direction, and then with the next link, the other direction. I often tie them off with butcher’s string because I am poaching the sausages.
Poach the links in a big stockpot with steamy water; you want it to be about 160°F, which is below a simmer. Poach the links for 20 minutes. If you are going to finish them off right away and eat them, go for it. But if you plan on storing the bockwurst for a while, plunge the poached links into a big bowl of ice water. I scrub my steel sink first, then fill that up with ice water; works great. Let the links chill a solid 20 minutes.
Hang the sausages to dry in a cool place. If it is warm out or if you are smoking your links, hang for one hour. If you have a place where the temperature will not go higher than 38°F, you can hang them as long as overnight. I put them on a cloth uncovered in the fridge overnight, turning them over before I go to bed.
If you are smoking your sausages, get your smoker going while the sausages hang. Smoke the links for at least 2 hours, and as many as 5. I prefer a lighter smoke, so you can still taste the meat and spices. I'd smoke these over oak, but maple, pecan or a fruit wood would also work. Once the sausages have dried and/or smoked, put them the fridge until needed. If you are freezing the sausages, wait a day before doing so. This will tighten up the sausages and help them keep their shape in the deep-freeze.