Season the pork with the salt, spices and curing salt. Ideally let this sit in the fridge overnight. If using ground pork just mix the salt, spices and curing salt into the meat.
Grind the meat and mix in the cold red wine. Continue mixing and kneading for a good 5 minutes. You want this to become a cohesive mass. We are not making burgers so mix and knead away.
Prepare the interior garnish by melting the butter and sauteeing the mushrooms until the liquid from the mushroom evaporates. Add the shallots and saute for a few more minutes. Taste and season with a little salt. Add the parsley and the currants and duck confit and chill the mixture.
Add the cooled garnish to the meat along with the eggs, cream and flour. Knead for a few minutes to make sure you have a good bind.
If you have a sous vide setup, heat your water to 75 C (167 F). Make sure the container with the water fits the terrine mold with water coming at least ¾ of the way up the mold but does not get inside the terrine when circulating. Test it out before filling the mold with meat!
If you do not have a sous vide setup, heat your oven to 300 F. Place a baking dish or roasting pan filled with hot water that comes up ¾ of the way up your terrine mold of choice.
Line a terrine mold or loaf pan with plastic wrap (for a cooler presentation you can shingle thinly sliced bacon or pancetta or prosciutto in the mold instead of plastic wrap). Fill the mold with the meat mix. Fold the plastic wrap (or bacon or prosciutto or pancetta) over the top.
Cover the terrine mold with its top or with aluminum foil. Cook for 2 hours in the sous vide bath or about 1 hour in the oven bath. Start taking the temperature of the terrine about 45 minutes after starting to cook. When it hits about 64 C (147 F) in the center it is done.
Let it cool for about 30 minutes, place weights on the meat and put it in the fridge. What works well for me is a rectangular piece of cardboard that fits on the surface of the terrine. Wrap that in a couple of layers of aluminum foil. Now, lay a piece of plastic wrap on the surface of the cooked terrine then the aluminum rectangle and then add some weights. A couple of tomato cans usually work well.
When ready to serve. Unmold it, slice and enjoy with mustard, bread and various pickles.