Preheat your oven to 350°F (175°C) and lightly grease a muffin tin or line it with cupcake liners.
In a mixing bowl, combine the mashed bananas, rolled oats, milk, honey (or maple syrup), almond butter, and vanilla extract. Stir until the mixture is well combined.
Add in the baking powder, cinnamon, and salt. Mix again until everything is incorporated.
Gently fold in the dark chocolate chips, reserving a few to sprinkle on top later.
Using a spoon or a measuring cup, divide the mixture evenly among the muffin tin cups, filling each about 3/4 full.
Sprinkle the reserved chocolate chips and chopped nuts (if using) on top of each oat cup.
Bake in the preheated oven for 15-20 minutes, or until the edges are golden brown and a toothpick inserted in the middle comes out clean.
Allow the oat cups to cool for a few minutes in the tin before transferring to a wire rack to cool completely.
Notes
Serve warm or at room temperature, drizzled with honey and garnished with banana slices.