Directions

1. Heat oven to 425 F.
2. Line a nine-inch removable bottom tart pan with the pastry crust, prick the bottom with a fork, line with parchment paper and pie weights (or dry beans). Bake for about 10 minutes until the crust is almost set. Remove from oven, remove paper and weights.
3. With a silicone pastry brush, spread the Dijon mustard over the crust in a light layer – just enough to cover the bottom. This will add a hint of extra flavor and also fill the holes from pricking the crust.
4. Reduce the oven temperature to 375 F, return the crust to the oven and bake for an additional 5 to 10 minutes until the crust is dry.
5. Remove crust from oven and cool. Leave oven on at 375 F.
6. In a medium saucepan, add the butter and oil and heat over medium-low heat. Add the onion and celery, cover the saucepan with parchment paper and cook for a 2 to 3 minutes. Add a dash of salt to bring out the juices, followed by a dash of dried thyme. Set aside once cooked.
7. Blanch and refresh the julienned zucchini and carrot, draining immediately so the vegetables do not become water-logged. Dry the vegetables by wrapping in a towel.
8. To make the custard, whisk the eggs, add the cream and season with salt, pepper, nutmeg and cayenne. Whisk until combined. Set aside.
9. Place the tart on a rimmed baking sheet.
10. Assemble the tart by layering the onion and celery mixture in the bottom of the tart crust. Follow with a layer of the prepared and dry julienned vegetables. Season with salt, pepper, nutmeg and sprinkle the fresh herbs of your choosing evenly over the vegetables.
11. Pour the custard mixture over the vegetables. Top with the Gruyere and Parmesan cheeses.
12. Return the tart on the rimmed baking sheet to the 375 F oven, placing it on the lower rack of the oven. Bake until the filling is set, the pastry is slightly puffed, and the top is brown.
13. Remove from oven and allow the tart to cool for 10 minutes. Unmold tart and place on cooling rack.
14. Serve warm or room temperature.