Preheat oven to 180°C (160°C fan-forced) and lightly grease the base of a 23cm round tart tin, line base with baking paper. As a rule of thumb use a dinner plate 2cm larger in diameter than the tin as a template to cut a circle of pastry.
Line the tin with pastry, gently massage the pastry into the sides and base, allow a little extra pastry to sit above the rim.
Line with baking paper and fill to the top with baking weights or a dried pulse (eg. chickpeas) to support the sides and weigh the base down during cooking. Place tart on a baking tray in preheated oven and bake for 20 minutes. Remove from oven; check pastry is lightly golden around the edges before removing weights and baking paper. Return tart tin to oven and cook for a further 8-10 minutes or until base of tart is golden brown. Reduce oven temperature to 160°C (140°C fan-forced).
Meanwhile, heat butter and olive oil together in a medium saucepan over a low heat. Add the shallots, garlic, thyme and jamon, stirring until well coated. Cover and cook for 10 minutes, until the shallots are soft. Remove from heat and allow to cool.
Spread cooled shallot mixture over the base of the blind baked tart shell.
In a medium sized mixing bowl, combine the crème fraiche, eggs, salt and pepper together, whisking until well combined. Carfeully pour over the shallot mixture and sprinkle over the Gruyere cheese. Bake in the preheated oven for 25-30 minutes or until just set. Serve warm or at room temperature.