Use a large glass bowl for marinating the meat, you don't want the vinegar to react with the bowl, and glass is the best choice for that. Add the peppercorns, juniper berries, cloves, and bay leaves to the glass bowl.

Add the water and vinegar to the bowl.

Stir around a little bit.

Remove any excess fat from the meat. You don't have to get all of it, but any really thick pieces should be removed. You want to remove the silver skin as well, as this doesn't render out.

Cut the meat into large chunks.

Cut the onion into large chunks, making sure to remove any of the paper.

Add the meat and the onions to the glass bowl with the marinade. Make sure the meat is fully submerged.

Let the meat marinate in the refrigerator overnight, up to 24 hours. While the meat is in the fridge, I stir the meat several time, to make sure all pieces of meat get the same exposure to the marinade.

Remove the meat from the marinade, and put it on a plate lined with paper towels.

Remove the onions from the marinade, and put aside on a plate lined with paper towels.

Remove the bay leaves from the marinade, and put aside.

Strain the remaining liquid through a fine-mesh sieve. Feel free to part ways with the peppercorns, cloves, and juniper berries—they've done their job. However, hang onto that flavorful liquid; we'll use it later!

Gently and completely dry the meat and onions with a paper towel.

In a Dutch oven over medium-high heat, melt the butter.

Brown the meat in two separate batches, ensuring each piece is caramelized on all sides. Resist the urge to constantly move the meat around; letting it sit ensures an even and beautiful browning. Once one side achieves the desired color, flip the pieces to guarantee uniform browning on all sides. Once the first batch reaches perfection, carefully remove the meat from the pan and set it aside. Proceed with the second batch, repeating the process to achieve that golden-brown goodness.

After achieving that golden-brown goodness on the second batch of meat, add the first batch back to the pan. Introduce the onion to the mix and continue cooking for a few minutes, until the onion adopts a touch of color, imparting its flavor.

Incorporate the marinade liquid into the mixture and bring it to a boil. As the liquid reaches its boiling point, you might notice foam forming on the surface. Gently skim off any foam that appears, discarding it to ensure a pristine and flavorful result.

After removing the foam, add the bay leaves and reduce the heat. Cover the Dutch oven and let it simmer for 2 hours.

After a 2-hour simmer, the meat should effortlessly fall apart. Introduce the brown sugar, appelstroop, and speculaaskruiden, giving it a good stir to ensure a seamless blend of flavors.

Following that, crumble the ontbijtkoek or honey cake into the stew. Allow it to simmer until the cake completely dissolves and the liquid thickens to perfection.

Taste the sauce and adjust with salt, pepper, and possibly a bit more sugar according to your preferences.