For the brownies:

• Preheat the oven to 350ºF/180ºC/155ºC Fan 

  Grease 13x9 inch baking pan
• In a microwave-safe bowl, melt 1 cup dark chocolate chips on medium power in 30-second intervals until just melted
• Melt the butter in a medium saucepan over medium heat, stirring until melted. Remove from heat.
• Whisk in the sugar and brown sugar right into the pot. Once combined,  whisk in the eggs & egg yolks one at a time, then the vanilla & salt followed by the melted chocolate. 
• With a wooden spoon, stir in the flour and cocoa powder until evenly combined. Fold in the chocolate chips.
• Spread into the pan and set aside while you make the topping.
• For the topping:
• Cream together the butter, sugar and brown sugar until light and fluffy.
• Blend in peanut butter & golden syrup, followed by the egg.
• In a separate bowl, mix the flour, baking powder, and salt. Blend it into the peanut butter mixture. Mix until smooth.
• Crumble the peanut butter mixture over the brownie mixture in the pan.
• Sprinkle with chocolate chips.
• Place the pan in the oven and set your timer for 25 minutes. When the timer goes off, open the oven, pull the shelf out and gently shake the pan. If the brownie wobbles in the middle, it’s not quite done so slide it back in and bake for another 5 minutes until the topping is golden brown & the sides are just beginning to come away from the pan. remove from the oven and cool the brownies for an hour before removing from the pan and slicing.
• The brownies will keep in an airtight container for up to 5 days, and the brownies actually get even better after a day.