The first thing to do is to prepare the ingredients. It is very important that the powdered sugar and the ground almonds are well sifted so that there are no lumps in the dough afterwards. Especially in the almonds there are often small pieces that should not end up in the macarons afterwards.
Then you can continue with the egg whites. To do this, whip the egg white with the salt on a medium setting for about a minute until it is frothy. Gradually, the granulated sugar is added. I took extra fine granulated sugar here because it dissolves faster than normal sugar. The egg white must then be beaten at the highest level until it retains its shape and the sugar is dissolved. In the next step, half of the powdered sugar and almond mixture is lifted under the egg whites. When everything is mixed well, the other half is added. At this point you have to be careful not to stir the egg whites for too long, because it will collapse more and more and will not rise nicely afterwards. Then the mass is filled into piping bags (putting the empty piping bag over a glass helps with filling) and placed on the baking paper. I still left some space to the edge because the macarons are getting a little bigger in the oven. After the macarons are on the tray, you can shake the tray a little or tap it lightly on a table so that any air pockets can escape from the mass and the tips are smoothed out from the splash.
Before they can be baked, however, they must dry for ¾ - 2 hours. If you touch the macarons (without pressure) they should no longer stick to your finger. This step is very important because otherwise the macarons will not have a straight surface, but rather a round one and cracks can appear. Explanation: The dried-on skin is pushed upwards by the moist inner rest of the dough when it rises in the oven, so that the typical macaron feet emerge.
After the resting time, they are baked at 130 ° C for 14-16 minutes. To ensure that they bake evenly, it makes sense to turn the baking tray after about seven minutes so that the heat is evenly distributed. After baking, they have to cool down completely before they can be filled. They harden as they cool down.
This time is perfect to prepare the filling. To do this, the Oreos are finely crumbled. This works best with a blender. These crumbs are then mixed with the powdered sugar. The soft butter is stirred until creamy and then the powdered sugar and oreo mixture is gradually added. When everything has been incorporated, the cream should be whipped for another two minutes at the highest level. Then it can be filled into a piping bag and spread over the macarons.