Preheat the oven to 350°F (180°C). Lightly grease a 1.5-quart baking dish (about 9×7 inches / 23×18 cm).
In a large bowl, mash the bananas until smooth.
Add the soy milk, espresso (or strong coffee), maple syrup, cashew/almond butter, vanilla, and apple cider vinegar. Mix until combined.
In a separate bowl, stir together the rolled oats, cocoa powder, protein powder (if using), baking powder, baking soda, and salt.
Pour the wet ingredients into the dry ingredients and stir well until combined.
Transfer the batter to the prepared baking dish and smooth the surface.
Bake for 35 to 40 minutes, or until the center is set and the top is golden brown.
Leave the oats in the dish to cool completely.
In a medium bowl, add the cashew or almond butter - warm in the microwave for 10 seconds to soften, then mix in vanilla to loosen the nut butter.
Add 1–2 tablespoons of the yogurt and stir until smooth.
Add the remaining yogurt, salt and optional protein powder. Mix until fully combined.
Taste test - add a dash of maple syrup if you want extra sweetness.
Once the baked oats are completely cool, spread the yogurt mixture evenly over the top.
Dust with cocoa powder just before serving.
