This is a great list of ingredient substitutions (which can add versatility and flexibility to your three-month supply). Some have multiple suggested substitutions -- they are numbered. I have a copy of this in my recipe book and inevitably end up consulting it regularly.

Cooking Substitutions:

Baking Powder (1 t.)
1) 1 t. baking soda plus 1/2 t. cream of tartar.
2) 1/4 t. baking soda plus 1/2 t. cream of tartar.
3) 1/4 t. baking soda plus 1/2 c. buttermilk (to replace 1/2 c. liquid in recipe).

Butter or Margarine (1 cup)
1) 1 1/2 c. margarine or butter powder.
2) 2/3 c. vegetable oil.
3) 1 c. shortening plus 1/2 t. salt
4) 2 sticks softened margarine plus 1/3 c. vegetable oil & 1/2 c. buttermilk. Beat until liquid is absorbed. Refrigerate.

Buttermilk
1) 1 T. vinegar (or 1 t. lemon juice or 1 3/4 t. cream of tartar) mixed in 1 c. milk.
2) 1 c. water, 1/3 c. powdered milk, 1 T. vinegar or lemon juice.
3) 1 3/4 c. dry milk in 3 c. slightly warm water (shake or beat until blended). Cover an allow to stand at room temperature until clabbered (6 - 12 hours). Refrigerate.
4) 1 c. water, 1/3 c. powdered milk, 1 T. vinegar or lemon juice. Let mixture stand in a warm place until thickened (18 hours). Stir until smooth. Refrigerate.
5) A buttermilk freeze dried culture can be purchased at a grocery or health food store, and kept indefinitely.

Chocolate (one square)
1) 3 or 4 T. cocoa plus 1/2 T. fat (butter, margarine or shortening).
2) 3 T. cocoa plus 1 T. butter.

Corn Starch (1 T.)
2 T. flour.

Cream (1 cup)
1/3 c. butter plus 2/3 c. milk.

Egg
1) Combine 1 t. unflavored gelatin with 3 T. cold water and 2 T. plus 1 t. boiling water.
2) Dissolve 1 tablespoon unflavored gelatin in 1 tablespoon cold water, then add 2 tablespoons boiling water. Beat vigorously until frothy
3) 2 egg yolks plus 1 T. water.
4) 2 T. dehydrated eggs plus 2 1/2 T. water.

Evaporated Milk
1 c. water, 2/3 c. powdered milk

Fats/Oils
Applesauce (subtract some sugar), or Beans (cooked and mashed).

Flour, White (1 cup)
1) 3/4 c. whole wheat flour.
2) 7/8 c. rice flour.
3) 1 c. corn flour.
4) 1 c. corn meal.
5) 3/4 c. buckwheat.
6) 1/2 c. barley flour.
7) 3/4 c. rye flour.

Green Pepper (1 medium)
1/4 c. dehydrated green pepper.

Half and Half (1 cup)
1) 7/8 c. milk plus 1 T. butter.
2) 1/2 c. coffee creamer and 1/2 c. milk.

Honey (1 c.)
3/4 c. sugar plus 1/4 c. liquid.

Jello (3 oz.)
1 T. plain gelatin plus 2 c. fruit juice.

Ketchup (1/2 c.)
1/2 c. tomato sauce, 2 T. sugar, 1 T. vinegar, 1/8 t. ground cloves.

Milk, Whole (1 cup)
1) 1/2 c. evaporated milk plus 1/2 c. water.
2) 1 c. reconstituted milk plus 2 T. butter.
3) 1 c. water, 1/3 c. powdered milk

Onion (1 medium)
1/4 c. dehydrated onion

Sour Cream (1 cup)
1) 1 c. milk plus 1 1/2 T. vinegar. Let stand until mixture thickens and clabbers.
2) 1 c. plain yogurt.

Sugar (1 cup)
1) 3/4 c. honey (reduce liquid by 1/4 c. or add 1/4 c. flour).
2) 1 c. molasses.
3) 1 1/2 c. carob syrup.
4) 1 1/4 c. malt syrup.
5) Corn syrup (reduce liquid). 6) Brown sugar.

Sugar, Brown
Sugar & Molasses.

Sugar, Powdered (1 cup)
1 c. sugar and 1/2 t. cornstarch. Blend in blender until powdered.

Sweetened Condensed Milk
1) 1 1/2 c. powdered milk, 3/4 c. sugar, 1/2 c. hot tap water. Place hot water in blender. With blender going, add sugar and dry milk, blend until smooth.
2) 1 c. hot water, 4 c. powdered milk, 2 c. sugar, 1/4 c. butter. Blend in blender. Can be refrigerated or frozen.
3) 1/2 c. hot water, 1 c. powdered milk, 1 c. sugar. Blend in blender. Can be refrigerated or frozen.

Tapioca (2 t.)
1 T. flour.

Tomatoes, Canned (1 cup)
1 1/3 cups cut up fresh tomatoes, simmered 10 minutes.

Tomato Juice (1 c.)
1/2 c. tomato sauce, 1/2 c. water

Whipped Topping
1) 6 T. powdered milk, 1 c. boiling water, 2 t. unflavored gelatin, 2 T. cold water, 2-4 T. sugar, 1 t. vanilla. Dissolve the milk in the cup of water and scald (boil until milk forms a skin on top). Soak the gelatin in cold water. Combine the scalded milk, dissolved gelatin and sugar. Stir and chill in the refrigerator until it jells. Then beat the mixture until it acquires the consistency of whipped cream. Add the vanilla and whip again.
2) 1 c. water, 2/3 c. powdered milk. Chill. Add 1/2 t. lemon juice. Whip. Fold in 1 T. sugar to taste.

Wine
1) Use apple or grape juice minus some sugar.
2) Use broth and lessen the salt.

Yeast (1 package)
1 T. yeast.