1. Line the muffin sheets with muffin paper.
2. Melt butter, chocolate, and Splenda in microwave on high for 90 seconds.
3. Sprinkle walnuts on bottoms of cupcake papers.
4. Add peanut butter and half-and-half to chocolate mixture. Stir to combine.
5. Pour evenly into cupcake papers. Freeze for 20 minutes.
6. Remove cups from muffin paper and serve immediately.