Gelatine is a tried and tested gelling agent made from collagen of animal origin. It is often used in desserts, sauces and other dishes such as a mirror glaze glaze on Galaxy cake pops to thicken and gel them.
Even for baking beginners: this is guaranteed to work with gelatine. If you want to avoid gelatin for ethical or health reasons, you can replace it with plant-based alternatives such as agar-agar, pectin or cornstarch.