In a large dutch oven, or another large pot that is oven-proof, combine all of the marinade ingredients. Bring to a boil over medium-high heat, boil for 10 minutes, then cool completely.
Nestle the meat down into the cooled marinade, then cover and refrigerate for at least 48 hours and up to 2 weeks. Turn the roast each day to make sure all of the meat gets a chance to marinade thoroughly.
Remove roast from the marinade and pat completely dry using paper towels. DO NOT DISCARD THE MARINADE. Transfer the marinade to a bowl.
Wipe out the dutch oven and heat 2 tablespoons of olive oil in it over high heat. When the oil is hot, sear the roast on all sides until browned (about 2 minutes per side), then pour marinade into the dutch oven with the meat.
Bring the liquids to a boil, then cover and reduce heat to a simmer.
Simmer for 2 to 2 ½ hours, until meat is tender. Alternatively, you can transfer the dutch oven to a 350 degree F oven with the lid on for 2 to 2 ½ hours until the meat is done if you prefer.
Remove meat from the cooking liquids and set it aside on a cutting board to rest for 10 minutes.
Meanwhile, strain the marinade, discarding the solids and reserving the liquid. Return the liquid to the dutch oven.
Add the crushed gingersnap cookies to the reserved liquid. Cook and stir over medium-low heat for 10 minutes until thickened into a nice gravy. Taste and adjust salt and pepper as needed.
Slice the sauerbraten into thin slices and serve with the hot gravy poured over the top.