Something about the harvest season and the changing leaves compels us to put food up for the coming cold weather. I always find it helpful to have some "universal" recipes available that can be applied to whatever I happen to find in the market or have on hand.
This season, we have pickled just about everything pickle-able and have not been disappointed in any of the pickles we have sampled so far. Refrigerator pickles keep for at least a month or two, and can be made out of any vegetable or fruit that is firm-fleshed enough to withstand the treatment. Pickling solutions are usually half water and half vinegar. Use a commercial vinegar that has been adjusted to 5% acidity. Artisanal vinegars can be used for refrigerator pickles, but bear in mind that a lower acid content may give different results and may reduce the keeping time.
To the basic mixture you can add varying amounts of salt (a basic ratio is one teaspoon of salt per quart of liquid) and sugar. Sugar can equal the amount of vinegar if you desire a syrupy sweet pickle. All manner of spices may be added. I recommend using only whole spices as ground ones will make the liquid cloudy. Ginger, hot peppers, bay leaves, and garlic cloves may also be used to flavor the pickling liquid. As a general rule, make a volume of pickling liquid equal to the volume of the jar. That is, for a pint of pickles, make two cups of liquid, to insure that you have enough to cover the vegetables. You will have some liquid leftover that can be used to make salad dressing, for a smaller batch of pickles, etc.
The basic procedure for refrigerator pickles is simple. Wash a jar in hot, soapy water, and keep it hot in a warm oven while you prepare the vegetables. Select only perfect vegetables for pickling. Cut them into uniform pieces. Bring the pickling juice ingredients to a boil over medium heat, add the vegetables, remove from the heat, and allow to cool a few minutes. Remove the vegetables from the liquid and pack them into the prepared jar. Pour the hot pickling liquid over the vegetables. Apply a lid and set the jar aside to cool to room temperature before storing in the refrigerator.
A great technique for a small amount of fruit is to make a mostardo. This is a mustard sauce that can be varied infinitely to suit your taste. Let's say you picked a handful of wild berries or plums or persimmons while on a walk in the woods. Wash and chop the fruit, removing any large seeds or other inedible debris, but leaving skins on. Combine the chopped fruit with an equal amount of sugar in a small saucepan. Stirring constantly, bring the mixture to a boil and cook until it is slightly thickened. The time required for this will vary with the type of fruit. When the fruit and sugar mixture has a nice consistency, remove it from the heat. Add mustard to taste. For example, you might use a dry mustard, such as Colman's, mixed with a little water or a coarse-grained mustard such as Grey Poupon or your favorite mustard or a combination. You could dress it up with whole yellow or black mustard seeds. Store the mostardo in the refrigerator and use it to season pork or poultry, or as a sandwich spread.
The best way to preserve most wild mushrooms is to dehydrate them. However, some cannot be preserved by any practical method and should always be cooked fresh. Your best bet is to talk to the forager regarding the best uses and preparation methods for the mushrooms he or she is selling.
Nuts are in season in fall, also, and most people will have to rely on the market for their supply, as nut trees are typically enormous and require several years to bear a crop. If you are into indigenous foods, you can purchase black walnuts, hickory nuts, and wild pecans online. The links given are examples. Other sources are out there, also. Nuts can be frozen for about six months without losing quality. Store them at room temperature for about a month.