If you haven’t done so already, crush up the Oreo (I used a plastic baggie and rolling pin, but a food processor will work as well) and place in a bowl.
Pour the melted butter over the cookie crumbs. Mix well to combine; the texture will be like crumbly sand.
Birthday Cake Cheesecake Filling
In a mixing bowl, beat the cream cheese, heavy cream, sugar, and vanilla until smooth and creamy. Refrigerate for 45 minutes.
After chilling, gently fold in the sprinkles. Do not overmix or the sprinkles will begin to bleed, and you will get color streaks in the filling.
To Assemble
Line up your jars (or cups). Have all your ingredients ready to go.
These jars were layered as follows: Oreo cookie crust crumbles, cheesecake filling, Oreo cookie crust crumbles, and additional sprinkles.
Start by adding the cookie crust crumbles to the bottom of each jar. Press the crumb mixture down with the back of a spoon to form a crust.
Next, add your cheesecake filling. Fill a Ziploc sandwich bag with the birthday cake cheesecake filling and cut the corner off. Then squeeze the filling on top of the cookie crust. If the filling is uneven, gently tap the jar on the counter a few times to level it out.
Sprinkle the top with remaining cookie crust crumbles and sprinkles.
Twist on the lids. Refrigerate until ready to serve.