• Line an 8x8 inch (20x20 cm) metal pan with parchment paper so that there is an overhang around the edges. Or, line with aluminum foil (leaving an overhang around the edges) and lightly grease with cooking spray.

Brownie Layer

• Preheat the oven to 350F (180C) degrees.
• Add the chopped butter and finely chopped chocolate to a large heat-proof bowl. Microwave on medium power (not high powder, which is standard on many models) for 45-second intervals, stirring between each interval until smooth.
• Whisk in the sugar and vanilla extract. Then whisk in the eggs. Make sure the batter isn't still hot when adding in the eggs - otherwise they can scramble.
• Gently stir in the flour and salt.
• Pour the brownie batter into the prepared pan and smooth it out to the edges.
• Bake in the preheated oven for 20 minutes. The top should look set, and you should start to see it pulling away from the edges. Once the brownie is out of the oven, turn the oven down to 325F (160C) degrees.

Peanut Butter Cheesecake Layer

• As the brownie is baking, make the cheesecake.
• In a large bowl, beat the cream cheese and sugar until smooth.
• Beat in the peanut butter. Be sure to turn off the mixer and scrape down the sides of the bowl .
• With the mixer on a low speed, mix in the sour cream and vanilla extract.
• In a small bowl, whisk together the egg and additional egg yolk. Then with the mixer on low speed, beat the whisked eggs into the batter. Stop mixing as soon as the egg is combined.
• Spoon the cheesecake batter on top of the baked brownie and smooth the top. Be careful - the pan will be hot.
• Place the pan back in the oven and bake for another 30-35 minutes. When the cheesecake layer is done baking, it should look set on top, except for perhaps in the very middle. You may start to see small cracks around the edges. If you start to see cracks forming in the middle of your cheesecake, then it's definitely done baking.
• Turn off the oven and open the oven door. Cool the cheesecake in the oven (turned off with the door open) for 30 minutes. Then remove from the oven and continue cooling until the pan is room temperature.
• Cover the pan with aluminum foil and place in the fridge for at least 4 hours for the cheesecake to properly set. I typically do this overnight.

Chocolate Ganache

• Finely chop the chocolate into very small pieces and place in a heat proof bowl.
• Heat the cream until almost boiling (either in the microwave or in a saucepan while gently stirring).
• Pour the hot cream over the chocolate and let sit for 2 minutes. Then whisk until smooth.
• Remove the cheesecake from the fridge. If there's any condensation on top of the cheesecake, pat it dry with a paper towel.
• Pour the ganache over top and and spread it smooth. Place the bars back in the fridge for the ganache to harden.
• When ready to slice & serve. Lift the bars out of the pan using the overhang of the parchment paper/aluminum foil. Place the bars on a cutting board and slice using a sharp knife (not a table knife). Wipe the knife clean with a paper towel in between each slice.
• Store bars in an airtight container in the fridge.