Place parchment paper in a 9x12 or 9x13 inch pan so it covers the bottom and 2 sides (to facilitate the brownie removal). Butter the parchment paper or spray with baking spray and set aside.
In the bowl of a mixer fitted with the wire attachment, beat the eggs at medium speed until fluffy and light yellow, add the sugar and beat until combined. Add remaining ingredients, and mix to combine.
Pour the batter into the prepared pan and top with 20 Oreo cookies. Set aside.
Place cream cheese, sugar, egg and vanilla extract in a bowl and beat until blended. Pour cheesecake mixture over the Oreos. Sprinkle chopped Oreos on top. Bake at 350 degrees for about 40 - 50 minutes until cheesecake is settled. Rotate pan half thru baking. The cheesecake should not be jiggly in the middle and the sides should look golden brown.
Bring a medium saucepan half filled with water to a boil. Place chocolate in a medium bowl set over the saucepan of simmering water, let it melt, stirring just a few times. Make sure the bowl doesn't touch the boiling water, to avoid overheating. When melted, remove bowl from heat and using a spoon pour the chocolate over the cheesecake layer.
Garnish immediately with chopped mini Snickers and crushed Oreos.
Let it cool to room temperature and place in the fridge for 6 hours before serving.