grease muffin cups or line with paper liners, and set aside.
in a bowl, stir together buttermilk, all-bran and natural bran, let stand for 10 minutes. in separate bowl, combine molasses, oil, egg and vanilla and stir into bran mixture.
in large bowl, whisk all-purpose flour and whole wheat flours, brown sugar, flaxseeds, baking powder, baking soda, nutmeg, and salt. pour bran mixture over top. sprinkle with dried cranberries, and stir just until moistened. scoop by 1/2 cupfuls into prepared cups.
bake in centre of 375*F oven until tops are firm to the touch, about 25 minutes.
let cool in pan on rack for 2 minutes. remove from pan and let cool.
wrap separately in plastic wrap and freeze in airtight container for up to 2 weeks.