1. Combine the venison, fatback, Madeira, pate spice, salt, and pepper in a bowl, cover, and refrigerate overnight. Plump the cherries by leaving them in the brandy overnight.
2. The next day, place your food-processor blade, grinder tray and head unit, and any bowl you plan to use in the freezer for about a half hour before you continue with the recipe.
3. Drain the venison, reserving the liquid. Drain the brandy from the plumped cherries and add to the reserved liquid. In a saute pan, melt the butter and saute the garlic and shallots until soft. Add the reserved liquid. Bring to a simmer, skimming any scum that rises to the surface. Reduce the liquid to a syrupy consistency, being careful not to burn it. Set aside to cool.
4. Heat the oven to 300 degrees.
5. Make the forcemeat: Grind the venison and fat through a small die into a bowl set in a bowl of ice. Transfer the meat to the food processor, add the egg whites, and blend until smooth. Add the wine reduction and continue to blend until smooth. Transfer to a chilled bowl. With a rubber spatula, fold in the cream until fully incorporated. Fold in the cherries.
6. Wrap a spoonful of the forcemeat in Glad wrap and poach in hot water (160 to 170 degrees) until the center reaches 150 degrees. The terrine should taste slightly oversalted. Adjust the seasonings, as necessary.
7. Line a 11⁄2-quart terrine mold with plastic wrap, leaving enough overhang on the two long sides to fold over the top of the terrine. Next, line the mold with the slices of ham, again leaving enough overhang all around to cover the top when the mold is filled. Fill the mold with the forcemeat. Fold the ham and then the plastic wrap over the top, and cover the mold with its lid or aluminum foil.
8. Place the terrine in a high-sided roasting pan and fill the pan with enough hot water (150 to 160 degrees) to come halfway up the sides of the mold. Put the roasting pan in the oven and bake until an instant-read thermometer inserted into the center of the terrine registers 150 degrees.
9. Remove the terrine from the oven, take it out of the water bath, and set a weight of about 2 pounds on top of it. Let the terrine cool to room temperature, then refrigerate overnight, or for up to 1 week.