Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper. Grease a 9-inch tart pan with a removeable base.

Toss the potato with the oil and a good pinch of salt and pepper together on the baking sheet. Roast for 35 minutes, turning once during cooking, until the potato is browned and cooked

While the potato is cooking, heat a medium-large skillet over medium-high heat. Cook the bacon, stirring occasionally, until browned and crisp. Remove to a paper towel-lined plate with a slotted spoon. Discard all but 1 tablespoon of the bacon fat.

Heat the bacon fat and butter together in the same skillet over medium heat. Add the onion and a good pinch of salt and pepper. Cook, stirring occasionally, for 10 minutes or until softened. Add the garlic and cook for 3 to 5 minutes until the onion is browned. Add the sugar and stir until the sugar is dissolved and combined. Remove the onion from the heat. Stir in the thyme.

Reduce the oven temperature to 375°F (190°C).

Roll the pastry on a lightly floured surface until large enough to fit into the tart pan – base and side. Carefully lift the pastry into the tart pan and lightly press on the bottom and up side of pan; trim the edge.

Sprinkle half of the cheese over the pastry. Spread or dollop the onion over the cheese. Scatter the potato and bacon over the onion.

In a medium bowl, whisk together the cream, eggs, nutmeg and a pinch of salt and pepper. Pour into the pan. Sprinkle with the remaining cheese. Bake for 45 to 50 minutes or until the tart is set and the pastry is golden. Let cool before cutting into wedges to serve. Garnish with a few extra thyme sprigs if desired.