Mushroom quinoa tartlets with truffle oil

Pastry cases

• 80 g unsalted butter cut into pieces, plus extra for greasing
• 80 g brown rice
• 60 g buckwheat groats
• 50 g quinoa
• ½ tsp salt
• 1 ½ tsp xanthan gum
• 1 egg
• 40 g cold water

Mushroom filling

• 20 g dried mushrooms (porcini, shiitake, etc)
• boiling water, for soaking
• 1 garlic clove
• 2 tsp olive oil
• 60 g cream cheese
• 10 sprigs fresh chives, finely chopped
• 30 g walnuts
• 1 - 2 pinches salt
• 1 - 2 pinches ground black pepper
• 2 tsp truffle oil, plus extra for drizzling
• 150 g fresh mushrooms of choice, cut into slices
• fresh thyme leaves, for garnishing