Sprinkle ¼ teaspoon of ground saffron over 2 ice cubes in a small bowl and let them melt at room temperature.
In a large bowl, mix 1 cup of plain Greek yogurt, 1 large thinly sliced onion, ⅓ cup of extra virgin olive oil, the juice of 1 lemon, and the saffron water. Season with salt.
Add 900g of boneless, skinless chicken breasts, cut into 1½in / 4cm cubes, and coat well. Cover and refrigerate for at least 3 hours, or up to 24 hours.
Take the chicken out of the fridge 15 minutes before cooking and preheat a grill to medium-high. Thread the chicken onto skewers.
Grill for 5 minutes per side, until golden and the chicken reaches 165°F / 74°C.
