The first step of making yeast bread is to make sure that the yeast is alive. This is called proofing the yeast. This is one of the most crucial steps because, if the yeast is dead, it can’t leaven the bread. To proof the yeast, measure out the amount of milk or other liquid that’s specified in the recipe, and heat the milk to a temperature of 100° to 110°. You can heat the milk in the microwave if you wish. Microwave at HIGH for about 1 minute or until the milk reaches at least 100°. Add the warm milk to a large bowl, and stir in the yeast and the sugar. Let this mixture stand for about 5 minutes. Live yeast will begin to swell and foam or bubble a few minutes after it’s stirred into the warm liquid.