For Onion Garlic Filling: Melt butter in a large skillet over medium heat. Sauté onion and garlic in butter until onion is golden in color, about 10 minutes. Cool.
For Bread: Combine whole wheat flour, 1/2 cup all-purpose flour, undissolved yeast, sugar, flax seed and salt in a large mixer bowl. Add water, butter and egg. Beat on medium speed for 2 minutes. Stir in enough additional flour to make a soft dough.
Turn dough out on a lightly floured surface and knead until smooth and elastic, about 4 to 5 minutes. Cover and let dough rest 10 minutes. Divide dough into 2 equal pieces. Flatten gently or roll into 6 x 10-inch rectangles. Place crusts on greased baking sheet.
Whisk all ingredients for Sour Cream Filling together in a small bowl; top each crust with an equal amount. Spoon cooled Onion and Garlic Filling over sour cream mixture. Sprinkle with cheeses.
Bake at 375°F for 25 to 30 minutes, or until lightly browned. Serve warm.
Recipe Note: Bread may be made in bread machine on dough setting. Remove dough from bread machine and let rest for 10 minutes. Proceed with shaping and topping the bread.