Preheat the oven to 350°F (175°C). Line a quarter-sheet baking pan with parchment paper, leaving an overhang for easy removal.

Place the 2 cups rolled oats in the bowl of a food processor or blender and pulse/blitz until they reach a coarse texture similar to quick oats. Transfer the ground oats to a medium mixing bowl.

Decide which binder you are using: 1/4 cup peanut butter, 1/4 cup sunflower seed butter, or 1 egg. If using peanut butter or sunflower seed butter: combine the 1/4 cup honey and the 1/4 cup butter in a microwave-safe bowl and warm about 15 seconds (just enough to loosen; do not overheat). Stir until smooth. If using the egg instead of a nut/seed butter: warm the 1/4 cup honey briefly only if it is chilled; do not warm the egg. Beat the egg lightly before adding to the wet ingredients.

In a small bowl, mash the 1/4 cup very-ripe banana and stir in the 1 teaspoon vanilla extract (and the beaten egg here, if using the egg option). If using warmed honey + butter, add this mixture to the mashed banana/vanilla (or to the egg/banana mixture if using egg and you warmed only the honey). If using the optional 2 tablespoons brown sugar for more sweetness, add it to this wet mixture and stir until combined.

Add the 1/4 cup all-purpose flour, 2 tablespoons hemp seeds, 1/2 teaspoon cinnamon, the baking powder (as listed in the ingredient list), and 1/2 teaspoon salt to the bowl with the ground oats. Stir the dry ingredients until evenly distributed.

Pour the wet mixture into the dry ingredients and mix until combined. Use a spatula or spoon to bring the mixture together; finish by using clean hands to press and squeeze the mixture into a thick, sticky dough that holds together when pressed between your fingers.

Transfer the dough to the prepared baking pan. Use your hands to press it into an even layer about 1/4 to 1/2 inch thick, pressing it nearly to the edges of the pan. Use a knife to score the top to precut bars (cut almost through but not completely).

Bake in the preheated oven for 18–22 minutes, until the edges are lightly golden and the center is set.

Remove the pan from the oven and let the bars cool completely in the pan (cooling will finish setting them). Once fully cooled, press the knife all the way through the scored lines to separate the bars.

Lift the bars from the pan using the parchment overhang and store or serve as desired.