Preheat the oven to 400 degrees F. Line a baking pan with a silicone baking mat or parchment paper.
Chop butter into small pieces. Add the chopped butter to the flour mixture and knead with clean hands until only small pieces of butter remain.
In another bowl, combine the egg, creamy peanut butter, sour cream, and vanilla. Whisk until smooth. Pour the mixture over the flour mixture.
Use a spatula to place the slices two inches apart on the baking sheet.
Bake for 12-15 minutes, or until lightly golden and a toothpick inserted into the middle of a scone comes out clean.
Let the scones cool for a few minutes before transferring to a cooling rack. While the scones are cooling, prepare the chocolate drizzle.
Combine the chocolate chips and cream in a small pot over very low heat. Whisk constantly until the chocolate is completely melted. Whisk in the powdered sugar, about a quarter at a time, until fully combined.
Drizzle over the scones, stirring the chocolate mixture vigorously if it becomes hard to drizzle.
Serve warm or at room temperature. Store in a container on the counter for a day or two. Can be reheated in the microwave for 20-30 seconds a scone.
Cooling time is for serving warm.