1. In a large bowl, whisk together flour, flaxseed, sugar, baking powder, baking soda, and salt. Add buttermilk, egg, and butter and whisk until just moistened (batter should have some lumps; do not overmix). Fold in blueberries.

2. Lightly coat a large nonstick skillet or griddle with butter and heat over medium-high. In batches, drop batter by 1/4 cupfuls into skillet. Cook until bubbles appear on top and a few have burst, 2 to 5 minutes. Flip pancakes and cook until golden brown, 2 to 5 minutes. Repeat with more butter and remaining batter (makes about 12), wiping skillet clean between batches and lowering heat if necessary. Serve with butter and syrup.