Step 1Combine the wine, vinegar, onions, carrot, allspice, cloves, salt and pepper in large bowl.
Step 1Place the roast in a large, deep glass dish and cover with the marinade. Cover and refrigerate the roast 5 days, turning every day.
Step 2Heat the oil in a deep heavy pot over medium-high heat. Remove the roast from the marinade and wipe it dry. Reserve the liquid. Roll the roast in flour, then add it to the pot and brown it. Add the reserved marinade and bring to a boil. Cover, reduce the heat to low and simmer the roast 2 1/2 hours.
Step 3Remove the roast from the pot and skim the fat from the liquid. Strain the drippings and add enough water to make 3 1/2 cups. Return the liquid to the pot.
Step 4Crush the gingersnaps in a food processor or blender and mix in the sugar. Slowly add 1/2 cup of the marinade to make a paste, then stir the paste slowly back into the pot with the remaining marinade. Return the liquid to a simmer, stirring constantly until the sauce is smooth and slightly thickened, 2 to 4 minutes. Add the roast and simmer 10 to 15 minutes, stirring occasionally. Slice the meat and serve with the sauce.