Banana Bread Oatmeal

• 2 cup plain rolled oats
• 0.75 cup walnuts
• 1 tsp baking powder
• 1.5 tsp ground cinnamon
• 0.5 tsp salt
• 2 cup milk
• 0.25 cup pure maple syrup, plus 1 Tbsp more for serving
• 1 large egg
• 2 tbsp extra virgin olive oil
• 2 tsp pure vanilla extract
• 3 ripe bananas, 2 mashed and 1 sliced
• 1 tbsp smooth peanut butter for topping (optional)