Prepare vegetables and toast bread, if desired.

Place sliced tempeh in a small pan and cover with water. Bring to a boil and cook for about 8 minutes. Remove tempeh and drain the water.

Heat the oil in a skillet over medium heat. Add the tempeh and cook for 2 minutes on each side. Remove and season with pepper.

While the skillet is still hot, you can add the sauerkraut to warm it up and blacken the edges (or you can serve with cold sauerkraut).

Build the sandwich by spreading the mustard on the bread, and all stacking the veggies and sauerkraut on top of the tempeh.

Serve.

Note: You can make this sandwich ahead of time and reheat (350 F (180 C) for ~15 minutes) and it holds up very well.