There are lots of steps here. Don't freak out. One thing at a time. Let's start with the rye tortillas.
In a large bowl of a stand mixer with a whisk attachment (or with a hand mixer), whisk together flours, salt and baking powder until just combined. Then add butter (or oil) and water and mix until dough is smooth. Divide dough into 12 equal balls and cover balls with a moist towel. Let rest for 10 minutes. Roll out each ball into a round, flat tortilla, adding a touch of all-purpose flour if your balls are sticky (hehe) but not too much because we don't want the dough cracking.
Preheat a large sauté pan or cast iron pan to medium-high heat. Cook a tortilla for about a minute on 1 side, until lightly browned, then flip and cook for 30 more seconds until cooked through. Repeat with other tortillas. Keep warm in a tortilla warmer or just wrap with foil and reheat before eating. Store extras in a plastic zip bag.
Okay! The next step is easy. Mix together sauerkraut and jalapeño pieces in a medium bowl. Set aside.
Queso time! My favorite time. In a medium saucepan over medium heat, melt the butter. Then add in flour while whisking for 2-3 minutes until you have a light brown roux. The slowly pour in milk while whisking and continue whisking until you have a thick sauce. Lower heat to medium low and gradually add in cheese while mixing with a spoon. Then add in horseradish/mustard, dill, and salt to taste. Keep warm on very low heat.
Tacos!! Almost eating time. In a large bowl, whisk together flour, salt, pepper, garlic powder and paprika. Then add in beer and mix to combine.
When ready to fry, heat 2 inches of oil in a Dutch oven, large pot or deep frying pan to 350 degrees F. Set up a cooling rack over paper towels. Dredge fish pieces in flour, and shake off excess. Then dip one at a time in batter. Fry a few pieces at a time (don't crowd pot) until golden brown, about 4-5 minutes total. Season with extra salt immediately once they come out of the fryer.
Assemble tacos by placing fish in the tortillas, and topping with sauerkraut, queso and cilantro. Eat!!