Combine the oats, milk, PB2, 2 teaspoons of maple syrup, vanilla, salt and lemon juice, if using, in a small bowl or jar. Refrigerate for at least four hours, preferably overnight.
1/2 cup (47 grams) rolled oats, 1/2 cup (120 ml) milk, 2 tablespoons PB2 powder, 2-3 teaspoons maple syrup, 1/2 teaspoon vanilla extract, pinch of salt, splash of fresh lemon juice