Preheat your oven to 400°F (200°C). Wash and prick the sweet potatoes with a fork. Place them on a baking sheet and roast for about 45 minutes, or until they are tender. Allow them to cool for a bit, then scoop the flesh into a bowl.

In a separate bowl, whisk together the heavy cream, milk, sugar, egg yolks, vanilla extract, and salt until fully combined. Add the roasted sweet potato flesh and blend using an immersion blender or mash until smooth.

Pour the sweet potato custard mixture into the pre-made tart shell, smoothing the top with a spatula.

Bake the tart in the preheated oven for 30-35 minutes, or until the edges are set and the middle is slightly wobbly. Remove from the oven and let it cool completely.

Once the tart is cool, sprinkle a thin layer of sugar over the top and use a kitchen torch to caramelize it until golden and crispy. Alternatively, place it under the broiler for a few minutes, but keep a close eye on it!

Let the tart chill in the fridge for about an hour before serving to ensure the caramelized topping stays crunchy. Slice into wedges and enjoy this delightful dessert!