Grind the beef and lard together using a coarse grinder. Beat the minced meat gently but do not salt.
Cut the hamburger buns in half. Heat a skillet over medium-high heat, then toast the cut sides of the buns for 1-2 minutes until lightly browned. Remove and set aside.
Using a serving ring, form the minced meat into patties the same diameter as the hamburger buns.
In the same skillet over medium-high heat, add the olive oil and cook the patties for 2-3 minutes on each side until cooked through (internal temperature 71°C / 160°F).
In a small bowl, combine mayonnaise, sour cream, and Worcestershire sauce. Season with salt and pepper to taste.
Slice the onion into rings or half-rings. Place in a small bowl, drizzle with white wine vinegar, and let sit for 2 minutes.
Spread sauce on the bottom half of each bun, add lettuce, then place one or two patties on top. Season the patties with salt and pepper, cover with a slice or two of toast cheese, add some pickled onion and more sauce, then top with the second bun half. Secure with a wooden or bamboo skewer.
Serve immediately while the buns are warm and crispy and the patties are hot.