Mixed Pickles

This is a classic mustard pickle — chow-chow by another name — and the flavor logic is sound. The preserving method is not, and the problems are specific to this style of pickle rather than to canning in general.

• "And then can"The recipe gives no processing step whatever: the hot mixture goes into jars and is sealed, most likely by the open-kettle method common in cookbooks of this kind. The seal comes from cooling contraction alone, and nothing sterilizes the jar headspace or the underside of the lid. Home-canning guidance abandoned the practice long ago because spoilage organisms can survive it.
• The flour is the real obstacleThree-quarters of a cup of flour makes a sauce thick enough that heat moves through it by conduction rather than convection. Even in a properly timed water bath, the center of a jar of flour-thickened pickle does not reliably reach processing temperature. Modern tested recipes for mustard pickle either omit the starch or are formulated and timed specifically around it; a thickener cannot be added to an untested formula.
• Acidity cannot be verifiedCauliflower, onions, green beans and green tomatoes are all low-acid vegetables, and here they go in raw-ish and in bulk against three quarts of vinegar of unstated strength. Cider vinegar of this period varied in acetic acid content, and the vegetables carry their own water. There is no way to know the finished pH, which is the single number that decides whether a shelf-stable pickle is safe.
• "One small cup of salt"The overnight salting is what draws water out of the vegetables and firms them, and it is the one quantity in the recipe that most affects both texture and the final dilution of the vinegar. "One small cup" is not a measurement anyone can reproduce.
• "2 lbs. cucumber pickles"This most likely means small pickling cucumbers rather than cucumbers already pickled. It is worth noting only because the phrase can mislead modern readers into thinking a jarred product is called for.
• "Silver onions"Small white boiling or pearl onions, the silverskin type long used for pickling. They were a standard mixed-pickle component.
• If you want to make mustard pickleUse a current tested recipe from a food-preservation authority. The spicing here — mustard, turmeric, sugar and cider vinegar — is the whole character of the dish and translates directly.