Sift together flour, salt, baking soda, and cocoa powder into a separate medium-sized bowl. Use a fork or a whisk to ensure that the ingredients are mixed well after sifting. Set aside.
In a medium-sized mixing bowl or the bowl of a stand mixer, mix butter and sugar until fully combined. The end result should look like wet sand.
Melt the chocolate in the microwave or in a double boiler.
Once the melted chocolate is cool enough to touch, add it to the butter/sugar mixture and mix until just combined.
Mix in eggs and egg yolks one at a time until just combined.
Mix in oil, vanilla, and sour cream until just combined.
Add dry ingredients to wet ingredients in three additions, mixing until just combined after each addition.
Mix in water until just combined.
Fill cupcake liners 2/3 full and put in the oven.
Check for doneness at 18 minutes - a toothpick inserted into the center of a cupcake should come out clean. If they are not done, check again every three minutes until they are done.
Immediately remove cupcakes from the cupcake tin and place on a cooling rack or on the counter to cool to room temperature. Although they are really good when they are hot, be sure to wait until they are room temperature to give your evaluation.
Whip cream cheese and butter until light and fluffy, about 3 minutes on high speed with an electric mixer.
Mix in powdered sugar one cup at a time.
Min in vanilla extract.
Mix in crushed Oreos.
Pipe onto cooled cupcakes.
Use dark cocoa powder to mimic the Oreo flavor.
Use dark chocolate to keep the flavor as close as possible to an Oreo.