In a 2-cup bowl, measure 1/2 cup warm tap water (100°-110°F), add 2 teaspoons of sugar and 1 tablespoon of dry active yeast. Allow mixture to dissolve and proof (approximately 5-8 minutes). Yeast mixture should foam and almost fill a 2-cup bowl.
In a small saucepan, over medium heat measure 1-1/4 cups water, add vegetable shortening; stir to dissolve. Remove from heat and allow mixture to cool to lukewarm.
In a large mixing bowl combine the flours, sugar, xanthan gum, dry milk powder and salt. Blend well. Add yeast mixture to flour mixture. Blend well. Add shortening/water mixture. Blend well.
Using a heavy-duty hand mixer, add 2 large eggs and mix at highest speed for 2 minutes.
Pour dough into a lightly oiled bowl and turn to coat. Let rise in a warm place until doubled in bulk (approximately 1 to 1-1/2 hours). Return dough to mixing bowl. Beat 3 minutes on high.
Pour dough into prepared bread pan(s). Let rise until dough is slightly above top of pan(s).
Preheat oven to 400°F. Place bread pan(s) in center rack of oven and bake for 10 minutes. Place foil over bread and bake an additional 50 minutes (slightly less if making 2 small loaves).
Note: If you wish use all white rice flour. Measure ingredients very carefully. The dough appears more like cookie batter, rather than bread dough, so don't be alarmed.