In large mixing bowl at high speed, beat egg whites with cream of tartar until foamy. Add sugar, 2 Tbsp. at a time, beating constantly until whites are glossy and stand in stiff peaks. (If using granulated sugar, rub just a bit of meringue between thumb and forefinger to feel if sugar has dissolved.) Gently fold in almonds. Drop by tablespoonsful or pipe through pastry tube or food-storage bag onto lightly greased or lined (foil or waxed, brown or parchment paper) baking sheets. Bake in preheated 225° F oven until firm, about 1 hour. Turn off oven. Let stand in oven with door closed until cool, dry, and crisp, at least 1 additional hour. Store in tightly sealed container with waxed paper between layers. (If stored cookies lose crispness, bake in preheated 200° F oven about 15 to 20 minutes.) Makes about 60 cookies.

Variations: Use amounts listed for 1 batch of cookies. To make 2 variations at a time, divide meringue mixture equally between 2 bowls. Beat or fold 1/2 the ingredient amounts listed for each variation into 1 of the bowls. For all variations, omit ground almonds.

Brandy Alexander—Beat in 1/2 cup unsweetened cocoa, 2 tsp. Vanilla, and 1/2 tsp. brandy extract.
Cherry/Almond—Fold in 1 cup chopped, drained maraschino cherries and 1 cup chopped almonds.
Chocolate—Beat in 1/2 cup unsweetened cocoa and 2 tsp. vanilla.
Citrus—Beat in 2 Tbsp. grated orange peel, 1/2 tsp. lemon extract, and a few drops yellow food coloring.
Mint/Chocolate Chip—Beat in 1/2 tsp. mint extract and a few drops green food coloring. Fold in 1 cup semi-sweet chocolate morsels.
Rocky Road—Beat in 2 tsp. vanilla. Fold in 1 cup semi-sweet chocolate morsels and 1 cup chopped nuts.