Mexican Hot Chocolate Brownies

Preheat the oven to 350°F. Line an 8x8-inch metal pan with foil or parchment paper and spray with nonstick cooking spray.
In a large heat-proof bowl, add the butter, chopped chocolate, and sugar. Microwave for 30 seconds at a time, stirring in between, until melted. Let cool until slightly warm (~85°F), about 15 minutes.
Whisk in the oil, eggs, egg yolk, and vanilla extract.
In a separate medium bowl, whisk together the flour, cocoa, baking soda, cornstarch, cinnamon, salt, and cayenne until evenly combined, then stir the dry mix into the chocolate mixture until just combined.
Fold in the chocolate chips. Spread the brownie batter evenly into the prepared pan.
Bake for 35 minutes, or until a toothpick inserted into the center yields moist crumbs. Do not overbake.
Let cool in the pan completely, about 1 hour.

Once brownies have cooled, preheat your oven to the broil setting.
Place chocolate chips in a medium heat-proof bowl. Set aside.
In a small saucepan, bring the heavy cream just to a boil over medium-high heat. Pour the cream over the chocolate and let sit for 5-8 minutes, or until the chocolate has softened.
Stir the cream and chocolate together until the chocolate is fully melted and evenly mixed, adding cinnamon and salt to taste.
Allow the ganache to cool and firm up slightly, then place 2 tablespoons (30 grams) in a piping bag fitted with a small round tip or a small cut at the tip of the bag and set aside. Carefully pour the remaining ganache on the top of the brownies. Spread evenly across the brownies, then gently push the marshmallows into the ganache to cover the surface.**
Using the broil setting, place the pan back in the oven for about 90 seconds, or until the marshmallows are toasted to your preference (can also use a kitchen torch). Place brownies in the fridge to chill for about 30 minutes (with hot pad underneath).
Once ganache has set, use the piping bag to drizzle stripes of ganache across the brownies. Allow ganache to set before slicing. Store leftovers in the fridge in an airtight container for up to 3 days.