Good Question
A yeast cake is a type of leavening agent made from a mixture of yeast, sugar, and flour. It is used in baking to help dough rise and create a light and airy texture in breads, pastries, and other baked goods. Yeast cakes are typically dissolved in warm water or milk before being added to the dough mixture.
Milk or water will do it.
Your recipe should indicate where and how to add the yeast, but yeast does not dissolve well in milk (if at all). Yeast forms into large clumps when mixed directly with milk and will take much longer to activate. I made this mistake the first time I tried to substitute milk for water when making bread. The usual way of adding yeast to such a recipe is to fully dissolve the yeast in 1/4 cup of warm water (about 110 degrees Fahrenheit). If the water is not warm enough, it won't activate the yeast and if it's too warm, it can kill the yeast. One of my colleagues proofs the yeast in the usual way (1/4 cup warm water, 1 tsp sugar, 1 tsp yeast), then adds the rest of the yeast to the water, mixes the dry ingredients with the milk for the recipe, then adds the water-yeast mixture to that. He claims that it works perfectly. Of course, if you use 1/4 cup of water to dissolve your yeast, subtract 1/4 cup of milk from the recipe unless otherwise indicated. And also make sure you're using the proper yeast for whatever it is you are baking.
French breads are made without milk, sugar, and shortening
Milk, rice milk and soy milk are yeast-free products
Yes a yeast infection can look like milk.
Milk
Yes, just be careful with the baking temperatures and how dense you want the bread to be. Many white breads actually ask for warm milk instead of water.
There are many different types of bread and therefore many different ingredients and recipes. Flour and water would be two ingredients in almost any type of bread, and salt and yeast would also be in the majority of bread recipes.
The very simplest bread could be made of nothing more than flour and water. Most simple breads are made of flour, water and oil or some other type of fat and salt. There are endless variations from that basic mix. Some type of leavening, such as yeast, baking powder or baking soda, lighten the dough and allow air to be incorporated into bread through rising. Eggs, milk and sugar might be added for more richness and flavor, as well as different types of flour, whole or cracked grains, seeds, dried fruit, herbs and spices.
MILK SUGAR IS FERMENTABLE BY YEAST. BUT IT PREFERS SUCROSE (TABLE SUGAR). IT MOSTLY TAKES LONGER, UNLESS YOU HAVE A YEAST THAT HAS THE ENZYME SYSTEMS FOR LACTOSE (MILK SUGAR), WHICH SOME DOES.
Basically, bread is made of flour, yeast and water. Other ingredients are sometimes added (like sugar, raisins or extra flavours) or substituted (different kinds of flour can be used; some people use milk instead of water).