Comeback sauce: combine all comeback sauce ingredients to a medium bowl and whisk to combine well.
Store in a sealed container in the refrigerator for up to two weeks.
Broccoli: if you are using a head of broccoli, chop off the ends about 1.5 to 2 inches down from the tops of the leaves to create florets or small pieces of broccoli. This recipe does not use the large trunk of the head of broccoli. You should have around 1.5 cups of florets.
Now you need to decide if you are going to roast the broccoli or saute it in a pan on the stove.
Roasting broccoli: preheat your oven to 400 F (205 C). Add all of the florets to a large bowl and toss with 2 tablespoons of olive oil, salt, black pepper, and red pepper flakes. Arrange on a sheet pan and bake for 15 to 20 minutes. After the broccoli is roasted remove it from the pan to a cutting board.
Sauteeing broccoli: place a medium pan over medium heat and add 2 tablespoons of olive oil to the pan. When the oil is shimmering add the broccoli and cook for 3 minutes. After 3 minutes, add salt, black pepper, red pepper flakes, and finely minced garlic and cook for an addition 4 to 5 minutes or until the broccoli is starting to soften and might be getting a little browned from the heat. Turn off the heat and remove the broccoli to a cutting board.
Chop the broccoli into smaller sized pieces about the size of a nickel.
Sandwich assembly: add a generous layer of comeback sauce on the bottom slice of bread. Top with half of the cooked and chopped broccoli.
Then add a couple of spoons full of sauerkraut and half of the Swiss cheese. Complete the sandwich with more comeback sauce spread on the top slice of rye bread.
Grilling/griddling: preheat a large pan or griddle on the stove over medium-low heat. Butter the outside of the top of the sandwiches. After the pan or griddle has heated up for 4 or 5 minutes flip the sandwich over, butter side down, into the pan. Cook for 3 minutes on the first side.
Add butter to the top of the sandwich while it is in the pan. After 3 minutes on the first side, flip the sandwich again, butter side down, and cook for an additional 2 to 3 minutes on the second side. Depending on the color of the bread, you may want to flip and cook again a couple more times until the outside of the sandwich is golden brown and crispy.
Remove the sandwiches from the pan/griddle and allow them to rest on a cooling rack for 2 minutes before serving.
Serve and enjoy.