Remove the husks from the 12 cardamom pods. Place the seeds in a mortar and mash for 1-2 minutes. Add the juniper berries, fennel seeds, chilli flakes, garlic powder (or 2 cloves), cumin, peppercorns, salt, and marjoram. Pound all spices together for 2-3 minutes until well combined.
Cut the 500 g chicken breast into cubes. Place in a container or freezer bag with the 250 ml olive oil and spice mixture. Mix well to coat.
Refrigerate the marinated chicken for 45-60 minutes.
Heat a pan over medium heat. Add the marinated chicken and fry for 10 minutes until it reaches 74°C (165°F) internal temperature. Avoid high heat as the spices will burn and taste bitter.