Preheat the oven to 325 degrees Fahrenheit. Line a 12×18 inch sheet pan with foil and cover with nonstick cooking spray.
In the bowl of a stand mixer, beat the eggs, egg yolks and sugar on medium-high speed until light and thick, about 3 minutes. Add in the vanilla extract.
Microwave the butter in a separate bowl for about 1 minute. Stir in the oil and cocoa powder.
Using a rubber spatula, gently stir in the butter-cocoa mixture. Fold in the flour, baking soda, cornstarch & salt until combined. Stir in the chocolate chips and pork floss.
Spread the brownie batter evenly into the prepared pan.
Top with dollops of miso caramel and marble it into the batter with toothpicks to create swirls.
Place in the oven and bake for 30 minutes, or until the brownies are set and a toothpick inserted into the center has moist crumbs attached. Do not overcook. Let cool completely before cutting and serving.