Buckwheat mushroom tartlets

Pastry

• 200 g buckwheat groats
• ¼ tsp salt
• 100 g unsalted butter, cut into pieces
• 50 g water
• 1 egg yolk
• gluten free flour mix, for dusting (see Tips)

Filling

• 40 g Parmesan cheese, cut into pieces (3 cm)
• 300 g fresh Swiss brown mushrooms
• 1 brown onion, cut into quarters (approx. 130 g)
• 1 sprig fresh flat-leaf parsley, leaves only
• 20 g unsalted butter
• 20 g vegetable oil
• 1 tbsp gluten free flour mix
• 100 g full cream milk
• 1 egg
• 50 g thickened cream
• 1 tsp salt
• ¼ tsp ground black pepper
• 1 pinch grated nutmeg
• 10 sprigs fresh chives, finely sliced, for garnishing