Grind instant oats using a food processor to yield 1 1/2 cups oat flour.

Whisk oat flour, baking powder, cinnamon, and salt together in a medium bowl. Add banana, cashew milk, egg, and avocado oil and whisk until just moist. Stir in raisins and walnuts. Let batter rest while griddle preheats.

Heat a lightly oiled griddle over medium-high heat. Drop batter by large spoonfuls onto the griddle and cook until bubbles form and the edges are dry, 2 to 3 minutes. Flip and cook until browned on the other side, 2 to 3 minutes. Repeat with remaining batter.