Step 1

Preheat oven to 180C. Grease a large baking dish.

Step 2

Using a knife or mandolin, slice potatoes and zucchini into thin rounds. Very finely slice the onion.

Step 3

In a large bowl, whisk together cream, garlic and mustard. Add vegetables and stir to coat well in the cream mixture.

Step 4

Layer potato and zucchini slices in prepared baking dish. Pour over any excess cream and onion. Cover with foil and bake for 45 minutes until potatoes are tender. Remove foil and sprinkle over cheese. Return to the oven for a further 25 minutes until golden and bubbling.