Melt butter and chocolate chips in bowl over double boiler. Stir until smooth and completely melted. Set aside to cool for 3 minutes.
Combine sugar, eggs and vanilla in medium size bowl. Whisk until combined. Add cooled melted chocolate and stir until completely incorporated.
Sift flour, baking powder, salt and cocoa powder over chocolate mixture, stirring until just combined.
Spray non-stick spray inside 12 ounce ceramic, microwave-safe mug. Spoon batter into mug. Press chocolate truffle in the center of batter.
Microwave on full powder for 1 minute and 45 seconds to 2 minutes. Let sit for 2-3 minutes. Add a scoop of vanilla bean ice cream and sprinkle crushed Heath Bar on top. Serve immediately.