Baked Steel Cut Oatmeal with Almonds and Almond Milk

Name: Baked Steel Cut Oatmeal with Almonds and Almond Milk
Ingredients: 3/4 cup steel cut oatmeal; 1/2 cup sliced almonds or other nuts, see notes above; 1 teaspoon baking powder; 1/2 teaspoon kosher salt; 1.5 teaspoon cinnamon, optional (I omit); 1 apple, peeled and thinly sliced, see notes above; 1 egg; 2 cup unsweetened almond milk or other nut milk, see notes above; 1/4 cup maple syrup; 2 teaspoon vanilla extract; 3 tablespoon unsalted butter, melted, optional (I omit)