Peel the ginger and garlic, then finely dice them. Puree with the yogurt.
Season the yogurt mixture with a pinch of salt, black pepper, and chilli flakes.
Place the chicken breasts in a freezer bag, pour in the marinade, seal the bag, and mix well. Refrigerate for 8-12 hours.
Remove the chicken from the refrigerator. Place each chicken breast on a piece of aluminum foil. Season with salt and pepper, and add a bit of the marinade if desired.
Fold the aluminum foil tightly to enclose each chicken breast. Place the parcels on a baking tray.
Preheat the oven to 200°C (392°F). Cook the parcels for 30-40 minutes until the chicken reaches 74°C (165°F) at the thickest point.
Carefully open the foil parcels and slice the chicken.