Within the bounds of common sense, you can switch stocks and meats within recipes. Vegetable and chicken stocks are a good foundation for most anything, while fish stocks should probably never be used with the flesh of a land animal.

In a pinch, you can use vegetable waters from last night's green beans or potatoes--or water with big glugs of wine in it--or just plain water.

Vegetables--unless they are strongly flavored and would overtake the taste of other ingredients--can be easily interchanged, or just left out.

Herb substitutions should be handled with a light hand. Mint instead of tarragon might be just awful. But parsley or celery leaves will always add the color you want and complement, rather than clash with the final product.

Oils, butter, lard, chicken fat, drippings, and bacon fat can at least be considered as substitutions for each other in the preliminary stages of sauteeing, but they can certainly change the seeming character or nationality of a dish.

Sometimes, though, you just plain don't have critical elements for what you want to do. In that case, I offer the following substitutions for you to consider:

• 1 cup sour cream = 1 cup yoghurt = 1 and 1/3 cup melted butter stirred into 3/4 cup of sour milk (this sour milk is made by mixing 1 Tbsp. of lemon juice or vinegar into lukewarm milk and letting it sit for at least 5 minutes)

• 1 cup whipping cream = 1/3 cup butter shaken up with or beaten into 3/4 cup whole milk

• As thickening agents, 1 Tbsp. flour = 1 and 1/2 tsp. cornstarch or potato starch or rice starch or arrowroot = 2 tsp. fine or quick-cooking tapioca

• 1 Tbsp. fresh grated ginger (and the whole root lasts forever in the freezer, ready for grating) = 1/8 tsp. powdered ginger

• 1 Tbsp. fresh herbs = 1/2 tsp. dried herbs

• 1 Tbsp. fresh horseradish (which also keeps forever in the freezer for grating) = 2 Tbsp. bottled horseradish, drained

• 1 tsp. lemon or lime juice = 1/2 tsp. vinegar

• 1 pound fresh mushrooms = 3 ounces dried mushrooms, reconstituted in tepid water