Make sure you're using your sharpest knife and cut off the outer layers of the kohlrabi until you only have the flesh remaining (the white part). This can be tough as the skin is quite hard but go slow and you'll get there.
Once you've taken the skin off your kohlrabi, cut into bite-sized pieces, about 2cm cubes.
Place a heavy-based frying pan, that has a lid, over medium heat and heat your coconut oil. Once melted, add your garlic and fry for 1 minute. Your garlic will be nice and fragrant, you can now add your kohlrabi cubes and sage and fry for 3-4 minutes.
You'll notice the edges start to brown, add 2-4 tablespoons of water, and cover. Cook for 8-10 minutes, or until your kohlrabi is soft, and you can easily pierce it with a fork.
Remove the lid and fry for an additional 2 minutes, remove from pan and set aside.
Sprinkle your crushed pistachios over your kohlrabi and serve hot.