Combine milk and vinegar in a small bowl and set aside 5 minutes.
Whisk together dry ingredients in a medium bowl. Add oil, banana puree, walnuts, and milk mixture. Whisk until smooth.
Heat a griddle or nonstick pan over medium-high heat. Grease griddle with coconut or vegetable oil over medium heat.
Pour cakes and cook for about 2 minutes, or until little bubbles form on edges of cakes. Flip and cook another 1–2 minutes. Reduce heat if needed to allow cakes to cook through without getting too brown. Serve immediately or keep hot in a warm oven until ready to serve.
For sauce, add coconut oil and sugar to medium nonstick pan over medium high heat. Let sugar melt. When it starts to turn golden brown, add syrup, which will bubble. Add bananas, walnuts, and salt.
Stir gently until mixture has a golden crust.
Top griddle cakes with hot caramelized sauce.
