- Make the red wine-pickled onions: In a pot over medium-high heat, combine vinegar, wine, sugar, and fish sauce with 1 cup water and bring to a boil. Toast marjoram, juniper, cloves, allspice, fennel seed, and coriander. Pulverize mixture in a spice grinder, then add to liquid mixture. Add bay leaf and chile to liquid. Remove pot from heat. Place onions in an airtight container and top with pickling liquid. Cover with lid, refrigerate, and allow to sit for at least 1 week.
- Make the horseradish dijon: Combine all ingredients and mix well. Set aside.
- Assemble the sandwich: In an oven or toaster oven, toast rolls whole, then cut in half. In a bowl, combine arugula, onions, olive oil, salt, and pepper. Spread horseradish dijon on both halves of rolls, then build sandwich by layering meat and arugula mixture.