Heat milk on medium-low temperature in a heavy-bottom pan to 180°. (If you don't have a heavy-bottom pan, heat over low temperature to avoid burning your milk. You can turn it higher, just make sure to stir occasionally.)
2 qt. milk
Remove from heat and let it cool to 130°.
Meanwhile soak gelatin in cold water, let is sit for a few minutes. Then add to 130° milk.
1 Tbs. unflavored gelatin, 1/3 c. cold water
Mix yogurt starter and sugar, and add to milk.
1/4 c. active yogurt, 1/2 - 1 c. sugar
Add vanilla. Stir until it is smooth.
1 Tbs. pure vanilla extract
Pour the warm mixture into sterile pint or quart-sized jars. Place lids on top, but do not tighten.
Place in a warm area, undisturbed, for 8 - 12 hours.
Screw on the lids and chill.
To begin the process again, save a small jar of yogurt for your next starter. However, after using your starter for about four or five batches, you need to buy another container again to use as a fresh starter.