Melt 1/2 oz (15gm) coconut oil in a pan, add the 1 chopped onion and cook gently until soft and golden. Add the garlic and cook for another minute or so. Season with salt and pepper to taste. Add the wine, turn up the heat and reduce the volume a bit. Remove from heat.
In another pan melt the remaining 1 oz (30 gm) of butter. Add the flour, stir and cook for about five minutes.
Now add the milk to the flour. Add the milk slowly while continuing to stir! You will end up with a nice thick sauce.
Mix in the onion and garlic and the sauce is ready.
Cut the chicken into rectangles as much as possible. Shouldn't be too thin so it can go onto the skewer, but too thick and it takes a long time to cook, I'd say 3/4 inch (1cm pieces).
Put the chicken into the sauce and let sit in the fridge over night. (If your in a rush, 2-3 hours in the fridge.:).
Cut the remaining onions into pieces.
Skewer the chicken/onion. (You can other veggies here if you like, depending on what your side will be).