2. Cut the puff pastry into a circle if it is not already. Fit the puff pastry in a tart or pie pan, prick all over with a fork and bake for 10 minutes. Set the crust aside and reduce the oven temperature to 350 F / 175 C.
3. Wash the carrots and courgette well. Peel the carrots then slice into long strips, along with the courgette.
4. Spread the tart crust with the mustard. Starting from the outside edge and working in, arrange the courgette and carrot strips upright and alternate in a circular pattern on top of the crust. If using cheese, add it now, using it to fill the gaps. Gently brush the top of the tart with olive oil and bake for 30 minutes.
5. If not using cheese, mix all the sauce ingredients together and spoon into the gaps of the baked tart, once the tart has slightly cooled.