Heat 3 inches of water in a large pot over high heat, adding 2 tablespoons baking soda. While heating, remove stems and produce stickers from the apples.
When water is near but not quite boiling, turn off heat. Put 3 of the apples in the water for 1 minute, turning a few times to cover both sides of the apple. Don't leave more than 1 minute in the water, or they will start to get mushy! Remove and immediately scrub with a coarse paper towel or towel. Repeat with other 3 apples. Make sure apples are fully dry. This step is important as will get off all the wax on the outside of the apple that can prevent the caramel from sticking to the apple.
Once apples are cleaned and dry, insert the popsicle or kabob sticks in the top of the apple. I prefer kabob sticks, as they look fancier, and are usually easy to find in the baking isle.
Ensure the caramel you are using is thick enough to stick on apple but thin enough to dip the apples in. If you are using my homemade paleo caramel (see notes for link), it's important the caramel has been in the fridge overnight to be thick enough to stick. Most store-bought caramel dips are thick and might need to be heated up slightly in the microwave to be dip-able.
Holding onto the stick, dip the apple in the caramel, rotating to ensure full coverage. Let excess caramel drain before placing on a sheet of parchment paper. I gently shake the apple to help the excess caramel drain back into the caramel bowl or pan. Repeat with all apples.
Let caramel apples cool in the fridge until caramel is no longer sticky to the touch. Length of time will vary greatly depending on type of caramel used.
Once cool, heat the white chocolate in a glass dish in the microwave for 1 minute. Stir, and then microwave another 30 seconds and stir again. Chocolate should be melted and smooth. If not, repeat for another 30 seconds, being careful not to overheat and burn!
Finely crush the Oreos into small crumbs. I do so with a food processor or mini food processor, but you could also do it with a kitchen hammer or rolling pin and some determination.
For the next layer, tilt the caramel apple on it's side and roll in the melted chocolate. Hold over the bowl and drain excess chocolate. Then, gently roll or press Oreo crumbs onto the white chocolate layer. This part will get messy and I do over a piece of parchment. Place upright on another piece of parchment paper and repeat with other caramel apples.
Put back into the fridge to cool until white chocolate is hard.
Once hardened, melt the semi-sweet chocolate chips in the microwave for 1 minute. Stir and then microwave again for 30 seconds. Stir until smooth. Repeat for another 30 seconds only if needed.
For the last semi-sweet chocolate drizzle, I put the melted chocolate into a disposable ziptop bag, pushing it all over to one bottom corner and then twising above it to create like a frosting tube. Cut off the bottom corner and then drizzle over the top of the white chocolate later. You can also just use a spoon to drizzle this layer, this is just how I get consistent, professional looking results.
Cool one more time in the fridge until all layers are hardened. Keep in fridge for 3-4 days. To eat, cut into slices, cutting around the stem/core. Enjoy!