Preheat the oven to 375 degrees Fahrenheit (190 degrees Celsius). Lightly grease an 8x8 baking dish or line it with parchment paper.
In a large bowl, mash the bananas until mostly smooth.
Add the plant-based milk, brown sugar, and vanilla extract. Stir until fully combined.
Add the oats, cocoa powder, baking powder, cinnamon, and salt. Mix until everything is evenly incorporated.
Fold in the vegan chocolate chips, if using.
Pour the mixture into the prepared baking dish and spread it out evenly.
Bake for 35 minutes, or until set in the center.
While the oatmeal bakes, gently warm the peanut butter in the microwave for 20 to 30 seconds until pourable.
Remove the baked oatmeal from the oven and drizzle the warm peanut butter over the top.
Let cool for 5 to 10 minutes before serving.
Notes
To adjust consistency: More plant-based milk = softer, looser oats. A little less plant-based milk = firm, sliceable. Don’t add too little, or it becomes rubbery.
For cake-like baked oats: Blending the oats into oat flour makes a fluffier, cake-like bake.
For individual serve: Divide the mixture between greased ramekins or a muffin tin and bake for 15-25 minutes (based on size).
Cool slightly: Just a few minutes helps it set/firm, becoming easier to slice and serve.