Gochugaru is the traditional spice used in kimchi; you’ll find it in any Asian market and most large grocery stores. Use it as a condiment, add as a topping on sandwiches or salads, stir into scrambled eggs, or add to stir-fry or fried rice.
1. Combine cabbage and radish in a large bowl; sprinkle with salt and toss to mix well. Let stand for 1 hour.
2. Combine garlic, ginger, miso paste, apple juice or water, chili powder, and sugar in a small food processor or blender, and process into a thick paste; add an additional tablespoon or two of apple juice or water if needed.
3. Add chili paste mixture and scallions to cabbage and radishes. Using rubber gloves, toss mixture with your hands, working chili paste into vegetables. Transfer mixture to two wide-mouth glass quart jars, pressing vegetables firmly into jars to compress them tightly. Cover each jar with a two-piece lid. Don’t screw the lid on with the ring, just set the ring over the lid to hold it down.
4. Place jars on a baking sheet to catch any liquid and let stand at room temperature for one to three days; insert a clean chopstick into mixture every day to release air bubbles, and top with additional sea salt and water brine if needed to keep vegetables submerged.
5. To store, stir ingredients to combine, screw lids onto jars, and refrigerate for 2 to 4 days. Store, refrigerated, for up to 6 months.