In a large mixing bowl, and using an electric mixer set at medium-high speed, beat the cream cheese until smooth. Add vanilla pudding and milk to bowl.
Beat in the condensed milk a little at a time, scraping the sides of the bowl, as necessary.
Beat in the lemon juice and vanilla. Once all beat together, set aside.
Break graham crackers in half, so you have 40 square pieces.
Take OREOS and chop them up so they are in smaller, bite-sized pieces.
Line the bottom of an 8x8 square pan with 10 graham crackers, and sprinkle with one-quarter of the crushed up OREOS. Layer in 1/3 of the cheesecake mixture. Repeat layering two more times.
Add a top layer of graham crackers and stick in the fridge while making the chocolate topping.
Make chocolate fudge ganache by stirring brown sugar and cocoa powder together in a small bowl, and set aside.
In a medium sized saucepan, over medium heat, add butter and milk, and bring to a slow boil. Let it boil 3-5 minutes. Stirring occasionally. Add cocoa and brown sugar mixture, and whisk until smooth, 2-3 minutes.Remove from heat. Stir in vanilla. Let sit 2-3 minutes to cool slightly.
Remove cake from fridge, and then pour fudge ganache sauce over the cake, and then sprinkle with remaining crushed OREOS.
Cover with plastic wrap, and refrigerate until firm, 2 1/2 to 3 hours.