What did dad say when his son headed to FLIP burger boutique? “Bison.” Yessir, a grassroots movement first stampeded National Bison Day through Congress in 2012, and bison devotees are upholding the annual tradition. FLIP rounds up the range for a brawny Big Bison burger: eight-ounce bison patty, bibb lettuce, tomato, cheddar cheese, caramelized onions, bacon, fried egg and FLIP sauce ($16). Corral a side of sweet potato tots with coffee BBQ spice or blue cheese dressing. Follow the National Bison Legacy Act.