Step 1

Whisk all-purpose flour, buckwheat flour, rye flour, sugar, baking powder, salt, and baking soda in a large bowl; transfer to a large jar.

Step 2

Do Ahead: Mix can be made 1 month ahead. Store airtight at room temperature.

Step 3

Place pancake mix in a large bowl. Whisk eggs and buttermilk in a medium bowl, then stir into dry ingredients just to combine (some small lumps are okay).

Step 4

Heat a griddle or a large skillet over medium; lightly coat with butter. Working in batches, scoop batter onto griddle. Cook pancakes until bottoms are golden brown and bubbles form on top, about 3 minutes. Flip and cook until cooked through and other side of pancakes are golden brown, about 2 minutes longer. Serve pancakes with maple syrup.