Trim and wash the runner beans. Cut them into even-sized pieces, about two inches long.

In a large bowl, combine the beans with the diced onions. A little sprinkle of salt over them allows moisture to come out, softening their sharpness.

In a saucepan, combine the white vinegar, flour, mustard powder, turmeric, celery salt, both sugars, smoked paprika, and black mustard seeds.

Heat gently while stirring. Use a whisk to combine until bubbly and well blended. This process usually takes about 5-7 minutes.

Bring a pot of water to a rapid boil.

Quickly blanch the beans and onion mixture for about 3 minutes, then drain them. This step softens them while keeping that satisfying crunch.

Pack the hot beans and onions into sterilized jars. Pour the hot brine over them, ensuring they are fully submerged.

Seal the jars tightly while they steam.

Allow the jars to cool at room temperature. Once cool, refrigerate them.

Let them sit for at least 48 hours to absorb all those fabulous flavors.