Mushroom, Leek and Sour Cream Tart with Walnut Pastry - Caroline Barty

Ingredients

• 90g walnuts
• 200g plain flour
• 100g butter, cut into cubes
• ¼ teaspoon fine salt
• For the filling
• 75g butter
• 2 medium leeks, trimmed, washed and finely sliced
• 2 x 200g packs woodland mix mushrooms (see intro)
• 4 eggs
• 2 teaspoons dried dill ( or 2 tablespoons finely chopped fresh dill)
• 300ml pot sour cream