Arrange apple chips on a large platter. Heat nut butter and chocolate in the microwave (or on the stove) until the consistency thins enough to drizzle over the apples. Drizzle the nut butter and chocolate evenly over the apples and top with chopped walnuts. Let stand at room temperature for 5-10 minutes to allow the chocolate and nut butter to harden slightly, then serve. This dish is best served within 10-20 minutes of assembly as freeze dried fruit becomes less crisp the longer it is exposed to air. (If the fruit is left out longer, it still tastes great, it just becomes less crisp)