Heat oven to 425 degrees. Butter baking sheet.
Mix flours, wheat germ, baking powder, baking soda, and salt in large mixing bowl or food processor. Add butter and cut in with pastry blender or process until butter bits are size of small peas. Mix 1/2 cup buttermilk and the honey, add to flour mixture, and stir or process until blended. (Do not overwork dough or biscuits will be tough.) Mix in more buttermilk, 1 T. at a time, until dough comes together and is just slightly sticky.
Flour sheet of waxed paper, place dough on paper, and flour top. Gently pat dough into 3/4-inch circle (about 6 inches in diameter). Flour sharp knife and cut dough into 6 even wedges. Arrange wedges at least 1/2-inch apart on prepared baking sheet. Brush tops lightly with beaten egg.
Bake biscuits until golden brown, about 15 minutes. Split biscuits horizontally while still hot. Serve with Tomato Cheddar Rarebit.