Heat a 4-quart soup pot or Dutch oven over medium heat. Add the ground beef, breaking it up as it cooks. Brown the beef for about 8–10 minutes until no pink remains.

While the beef is browning, place the ginger snaps in a heatproof bowl and pour 2 cups of hot water over them. Let soak for about 10 minutes.

Carefully drain any excess fat from the beef, then add the finely chopped onion to the pot. Stir and cook for an additional 3–4 minutes until the onion is translucent.

Stir in the ketchup, Worcestershire sauce, and ground black pepper into the beef and onion mixture. Mix well for about 2 minutes.

Pour the soaked ginger snaps and their soaking liquid into the pot, stirring until thickened and mostly dissolved for about 3–5 minutes.

Gradually add 4 to 6 cups of water, stirring to reach your desired thickness, mixing for about 5 minutes.

Bring the soup to a gentle boil, then reduce to low heat and let simmer partially covered for 1 to 2 hours, stirring every 20 minutes.

After simmering, lay the lemon slices on top and continue to simmer for another 10–15 minutes.

Remove the lemon slices and stir in the hard-boiled eggs and sherry wine if using. Cook for an additional 5 minutes.

Serve warm in bowls, garnished with fresh parsley if desired.