Put the broccoli, onion and 1 tbsp of the olive oil, with plenty of salt and pepper, into a shallow roasting tin. Stir to coat with the oil. Roast for 10 minutes.
Add the gnocchi, the remaining oil and stir well. Return to the oven for 10 minutes.
While it’s in the oven, mix the cornflour with just enough of the milk to make a smooth paste in a small bowl. Then stir in the crème fraîche and whisk until smooth. Add the rest of the milk and whisk again until smooth.
Add two thirds of the parmesan, the mustard, garlic granules and more salt and pepper.
Add the creme fraiche mixture to the roasted gnocchi, stir through and sprinkle the remaining Parmesan on top. Bake for a further 10 minutes.
Notes
Broccoli chunks: Chop the broccoli up into similar size pieces as the gnocchi so it cooks quickly and before it burns on the outside.