Make the Brownies

1. Preheat oven to 350 degrees. Grease a 9×13 baking pan, or line it with parchment paper that stick above the sides of the pan. You can use it to lift the brownies out of the pan later, if desired.
2. Whisk the oil, sugar and vanilla extract together until well combined.
3. Add eggs and whisk until well combined.
4. Combine flour, cocoa, baking powder, salt and espresso granules in a separate bowl.
5. Slowly add dry mixture to the egg mixture until well combined.
6. Pour the batter into the pan and spread evenly.
7. Bake for 20-25 minutes, or until a toothpick comes out with a few crumbs.
8. Allow brownie to cool completely.

Make Tiramisu Filling

1. To make filling, combine egg yolks and sugar in the top of a double boiler, over boiling water. If you don’t have a double boiler, you can use a metal mixing bowl set over a pot with simmering water in it.
2. Cook for about 6-8 minutes, with heat on low, stirring constantly, or until mixture is light in color and sugar is dissolved. If mixture starts to get too thick and a darker yellow, it’s overcooked
3. When done, whip yolks with mixer until they thicken and yellow a bit.
4. Fold mascarpone into whipped yolks.
5. Add heavy whipping cream to another mixer bowl and whip until stiff peaks form, about 5-7 minutes.
6. Fold whipped cream into mascarpone mixture.

Assemble

1. To assemble tiramisu, first add espresso granules to warm coffee in a small bowl and stir to dissolve.
2. Add Kahlua to espresso mixture.
3. Drizzle about 3 tbsp of Kahlua mixture over the brownie.
4. Spread half of the filling evenly on top of the brownie.
5. One at a time, dip Oreos and chocolate chip cookies into kahlua mixture and place them on top of filling. I did alternative rows of each cookie for two rows of Oreos and two rows of chocolate chip cookies. Your rows and number of needed cookies may vary depending on their size.
6. Top cookies with remaining filling, then dust with cocoa powder. Refrigerate until ready to serve.