Step 1: Prepare Vegetables. In a very large bowl or clean food-grade bucket, combine the chopped green tomatoes, cabbage, bell peppers, and onions. Sprinkle evenly with pickling salt and toss to coat. Let the mixture sit at room temperature for 4-6 hours, or overnight in the refrigerator, allowing the salt to draw out excess moisture.
Step 2: Rinse and Drain. After the salting period, drain the vegetable mixture thoroughly. Rinse the vegetables under cold running water to remove excess salt, then drain again very well. You can gently press them in a colander to remove as much liquid as possible, but avoid squeezing too hard, as you want to retain some crispness. This rinsing step is crucial for a balanced chow chow recipe.
Step 3: Prepare Brine. In a large non-reactive pot (stainless steel is ideal), combine the apple cider vinegar, granulated sugar, mustard seeds, celery seeds, ground turmeric, and red pepper flakes (if using). Bring the mixture to a boil over medium-high heat, stirring until the sugar is completely dissolved.
Step 4: Combine and Simmer. Add the drained vegetables to the boiling brine. Reduce the heat to medium-low and simmer gently for 20-30 minutes, or until the vegetables are tender-crisp and the liquid has slightly thickened. Stir occasionally to ensure even cooking and to prevent sticking. Do not overcook; the vegetables should still have a bite.
Step 5: Prepare Jars. While the chow chow is simmering, sterilize your canning jars and lids according to manufacturer's instructions. Keep them hot until ready to fill.
Step 6: Fill Jars. Carefully ladle the hot chow chow mixture into the hot, sterilized jars, leaving 1/2 inch of headspace. Remove any air bubbles by running a non-metallic spatula or knife around the inside of the jar. Wipe the rims clean with a damp cloth.
Step 7: Seal and Process. Center the hot lids on the jars and apply the screw bands finger-tight. Process the jars in a boiling water canner for 10 minutes (adjusting for altitude if necessary).
Step 8: Cool and Store. Carefully remove the processed jars from the canner and place them on a clean towel or cooling rack, ensuring they are not touching. Let them cool undisturbed for 12-24 hours. Check for seals; lids should be concave and not flex when pressed. Store properly sealed jars in a cool, dark place for up to 1 year. Once opened, refrigerate and consume within 2-3 weeks. This careful process ensures your chow chow recipe is preserved perfectly.