1. Preheat oven to 350°F (180°C). Line a 12-cup muffin pan with large, paper liners.
2. Stir flour with cocoa powder, baking powder and baking soda.
3. Beat butter and brown sugar in a spearate bowl until fluffy. Gradually beat in eggs, sour cream and vanilla until combined.
4. Using low speed, gradually blend in dry mixture and mix until combined. Slowly, pour in boiling water; scrape down sides of bowl and mix on low just until combined.
5. Divide batter evenly between lined cups. Bake for 22 minutes or until a tester inserted in centre comes out clean. Cool completely.
6. Frosting: Melt peanut butter chips in the microwave on MEDIUM for 1-2 minutes; stir until smooth. Cool to room temperature.
7. Beat butter and vanilla with melted chips until fluffy. Pipe or spread the frosting over the cupcakes; sprinkle with chocolate chips.
• Using a piping bag with a star-shaped tip gives these cupcakes their bakery-made look.