Spread the walnuts on a baking sheet and toast at 350°F (175°C) for 6 to 8 minutes. Or toast them in a dry skillet over medium heat for 4 to 5 minutes, stirring often. They are ready when they smell nutty and look a shade darker. Cool, then chop into pieces about the size of a lentil.

In a large bowl, whisk the flour, brown sugar, baking powder, cinnamon, and salt. Break up any sugar clumps with your fingers. Even distribution of the baking powder gives you an even rise.

In a second bowl, mash the bananas with a fork. Leave a few small lumps for pockets of banana flavor. Whisk in the milk, egg, melted butter, and vanilla. Let the butter cool for a minute first so it doesn't scramble the egg.

Pour the wet mixture into the dry and fold with a spatula until just combined. Small lumps are fine, and overmixing makes tough pancakes. Rest the batter for 5 minutes, then fold in the walnuts. It should be thick but pourable, like softly whipped cream.

Heat a nonstick skillet or griddle over medium heat and brush lightly with butter. Pour 1/4 cup of batter per pancake and leave room between them. Cook 2 to 3 minutes, until bubbles form and pop near the edges and the surface looks matte rather than wet. Flip once and cook 1 to 2 minutes more, until golden brown. If the first pancake browns in under a minute, lower the heat. Banana sugars scorch quickly. Keep finished pancakes on a rack in a 200°F (95°C) oven while you cook the rest.

Stack three pancakes per plate and top with sliced banana, a few extra toasted walnuts, and warm maple syrup. Serve right away, while the edges are still slightly crisp. Rebecca's Tip: Toast the walnuts and rest the batter for 5 minutes, and don't skip either one. Toasting removes the raw, tannic edge from the nuts. Resting lets the flour hydrate so the pancakes cook up taller and more tender. To keep leftover walnuts fresh, store them in the freezer, since their natural oils turn rancid at room temperature.