Remove the seeds and peel from the pumpkin, then cut into small pieces.
Place the pumpkin pieces in a steamer and steam for 15 minutes.
Mash the steamed pumpkin.
In a bowl, combine flour, butter, and sugar, rubbing gently by hand to make a streusel texture.
Place the mashed pumpkin in a baking dish and spread the crumble mixture on top.
Bake in a preheated oven at 180°C for 20 minutes.