Heat butter in a Dutch oven until hot, add 1 chopped onion, 5 cloves chopped garlic, 2 chopped ribs of celery, and 1 tablespoon peppercorns to the pot and cook, stirring occasionally, until onions begin to brown. Place corned beef on top of vegetables in pot. Add 12 ounces beer and enough water to just cover the beef.
Bring to a boil, then reduce heat to low, cover and simmer for 3 hours, or until fork tender. Once tender, remove from pot and let rest on a cutting board to cool before slicing. Slice thinly against the grain once cooled and divide into 4 mounds (servings) for sandwiches.
For the Russian Dressing:
Whisk all the ingredients together in a bowl, set aside if preparing sandwiches within a few minutes. If made in advance, refrigerate until ready to use, up to 1 week.
Preparing the Sandwiches:
Lightly butter the cut side of each bun and set aside. Fold 2 paper towels into a square and set in the bottom of a small bowl. Using a slotted spoon, place approximately 2 cups of sauerkraut in the bowl. Let kraut set in bowl to allow paper towel to absorb excess liquid.
Heat a cast iron skillet over med-high heat until hot. Place buttered buns on skillet and toast until golden browned and crisp. Set aside until ready to build the sandwiches.
Reduce heat to medium-low and place 2 piles of 1/2 cup servings of sauerkraut on the heated skillet and cover with a slice of Swiss cheese. Along side the kraut, place 2 mounds of meat. (A larger pan or griddle can make 4 at a time.) Allow to warm over medium low heat until lightly browned on one side.
While the cheese is melting on the kraut, carefully turn each pile of meat over with a spatula, using your hand to guide it over on the other side. Spoon about 2 tablespoons of dressing over the meat.
Once the cheese has melted and the meat is warmed with the dressing, assemble the sandwich by placing the mound of meat with sauce on a toasted bottom bun. Continue with the kraut and cheese by placing on top of the meat and sauce. Top with the other half of the bun.
Serve with extra sauce (and extra napkins) at the table.
Uncured corned beef brisket is unlike regular corned beef, the saltiness is less pronounced and the beef carries a milder flavor. Due to the absence of sodium nitrite, the beef will be brown when cooked rather than pink.Pressure Cooker Instructions:
Heat butter in pressure cooker over medium heat until hot and bubbly. Add onion, garlic, celery, and peppercorns to the pot and cook 8-10 minutes, stirring occasionally, until vegetables are soft.
Place corned beef on top of vegetables and pour in beer and enough water to just cover the beef. Place lid on cooker and bring to pressure according to manufacturers instructions.
Once at pressure, reduce heat to low to maintain a gentle release of steam, and cook for 50 minutes.
Release pressure and allow to cool naturally, about 10 minutes. Beef should be fork tender and ready to serve.