Warm up the air fryer by setting it to 400°F (200°C) and running it for about 3 minutes to create a hot basket.
Take the bratwurst links out of their packaging and dry them well with a paper towel to reduce surface moisture.
Lightly spray each brat with olive oil to help them brown evenly during cooking.
Place the brats separately in the air fryer basket, making sure there's space between each for proper air circulation.
Cook the brats for 8 minutes, listening for a consistent sizzling sound that signals proper searing.
Carefully flip each brat using tongs to ensure even browning on all sides.
Continue cooking for an additional 7 minutes until the brat skins look golden and tight.
Check that at least one brat has reached an internal temperature of 160°F (71°C) using a thermometer.
Remove the brats from the air fryer and let them rest for 3 minutes to allow the juices to settle.
Finally, spread stone ground mustard inside each brioche roll, add the rested brats, and top with sauerkraut and caramelized onions before serving.
