Prep the tempeh: 
Steam the Holy Plantz tempeh for 10 minutes, then slice into thin sandwich-style cutlets. Mix together the soy sauce, maple syrup, ketchup, smoked paprika, garlic powder, and pepper. Coat the tempeh slices in the marinade and let sit for 5-10 minutes.

Cook tempeh: 
Heat olive oil in a pan over medium-high heat. Cook the tempeh for 3–4 minutes per side until deeply browned, caramelized, and slightly crispy around the edges.

Make the sauce:
Mix all the sauce ingredients together until smooth.

Toast the bread:
Spread vegan mayo/butter on the outside of the bread slices and toast in a pan until golden and crisp.

Assemble:
Spread the sauce generously on the bread. Layer with crispy tempeh, plenty of sauerkraut, more sauce, then another layer of tempeh. Top with the second slice of toasted bread.

Serve:
Serve hot with pickles and chips. Best eaten immediately while the bread is crispy and the tempeh is warm.