2 cups sugar
1 cup heavy cream
1 teaspoon cream of tartar
1 teaspoon vanilla

Put sugar and cream in a heavy bottomed saucepan; heat and stir until it boils. Add cream of tartar, and boil, stirring carefully to prevent burning, to 238° F., or until candy forms a soft ball when tested in cold water.

Move thermometer often, so that the candy won't burn underneath.

When the candy thermometer reaches 238°F, pour the hot mixture out onto a cold marble slab or cookie sheet which has been slightly moistened with a damp paper towel, and leave until cold. With a wide silicone or metal spatula work the candy back and forth until it becomes creamy. This will take some time, but it will surely change, finally, if it was boiled to the correct temperature.

Cover with a damp cloth for half an hour, then add vanilla, working it in well, using clean hands. Press into a small shallow box lined with wax or parchment paper. Let stand until the fudge has hardened, then cut into squares.

Other flavors can be used instead of vanilla, and the candy may be tinted with food colorings to correspond.

The fudge can be divided into several portions, and each portion may be flavored and colored differently, and pressed into a pan in thin layers (a different color for each layer), then cut in squares when hard. Or press a nut half into each square, then place the square in a small candy paper and arrange in bon-bon boxes with other candies and chocolates to give as gifts.