In a large bowl or cooking pot, add the pumpkin pieces, sugar, orange juice, cinnamon stick, grated ginger, orange zest, and star anise.

Cover the bowl and let it rest overnight in the fridge, or on the counter if the room is cool.

The next day, place the pot over medium heat and bring to a boil.

Cook on high heat for 2–4 minutes, then lower to very low heat.

Let simmer for 20–30 minutes, stirring occasionally, and mash the pumpkin pieces with a potato masher if desired.

If you have a sugar thermometer, cook until it reaches 106°C (222°F).

Near the end of cooking, add the butter and stir.

Quickly transfer the jam into clean, sterilised jars. Seal immediately.