1. Place a medium skillet over medium heat. Add walnuts and cook, shaking pan often, until nuts are golden, 2 to 3 minutes. Transfer to a plate to cool.
2. Melt butter in same skillet over medium heat. Add apples, cinnamon and vanilla and cook, stirring frequently, until apples are soft, about 5 minutes. Stir in maple syrup and continue to cook until syrup thickens, 1 to 2 minutes longer. Transfer to a bowl and set aside for 10 minutes to cool slightly.
3. Divide ice cream among 4 bowls. Top with apples and sprinkle with walnuts. Serve immediately.