Dissolve the yeast in warm water to which you have added a pinch of sugar.
Let it stand about 10 minutes or until bubbly.
In a large bowl, mix together the warm milk, shortening, salt, and sugar.
Add the yeast mixture and then gradually add the soy flour, mixing as you go.
Beat for about 2 to 3 minutes.
Gradually add the all-purpose flour (you’ll probably need to use a large wooden spoon when the dough gets thick) until it forms a loose ball and pulls away from the sides of the bowl.
Turn out the dough onto a floured work surface and knead until smooth and elastic, about 8 minutes.
Place the ball of dough into a large greased bowl, turning the dough so the entire surface is greased.
Cover and set in a warm place to rise until double, about 2 hours.
Divide the dough in half and shape into loaves.
Place in greased loaf pans, cover, and let rise until the bread reaches about an inch above the top of the pan, about 45 minutes.
Bake in a preheated 375° oven for 35 to 40 minutes or until done.