The chicken drumsticks are sprinkled with salt and vacuum-sealed. They need 3 hours at 68 degrees Celsius (154 degrees Fahrenheit) in the sous vide/water bath.
Then take them out and pat them dry.
In the meantime, make a spice mix of flour, onion powder, garlic powder, paprika, salt, cayenne, and regular pepper mixed together in a shallow, wide container with a lid.
Take a tall and narrow bowl (or pitcher) and fill it with 1 liter of buttermilk. It's used to brine the meat lightly without making it salty.
Place the chicken drumsticks in the flour/spice mixture, then put the lid on and shake the whole container. This ensures that the flour/spice mixture penetrates all parts of the chicken, creating small cracks that give even more of the crispy surface.
Dip the chicken in the buttermilk for 5-10 seconds, then remove and place back in the other container. Again, put the lid on and shake the container.
Finally, fry the drumsticks in oil at 190 degrees Celsius (374 degrees Fahrenheit) for 40-60 seconds, depending on the color of your drumsticks. This can be done in a deep fryer or a regular pot/pan.
They will be both juicy and crispy and ready to serve.