Serves 4
40g butter
1 tbsp olive oil
1 leek, trimmed, thinly sliced
5 large flat mushrooms, sliced
2 tbsp tarragon leaves, finely chopped
2 sheets ready-rolled frozen puff pastry
sheets, partially thawed
1 egg, whisked
½ cup crème fraîche (or sour cream)
2 tsp grainy mustard
salt and pepper, to taste
1 Preheat oven to 200C. Grease and line the base of a 20cm cake tin with baking paper.
2 Melt butter in a non-stick frying pan with oil over medium heat. Add leek and cook, stirring occasionally, for 3 minutes or until soft. Transfer to a plate.
Increase heat to medium-high and add one-third of the mushrooms. Cook, stirring occasionally, for 8 minutes or until golden. Transfer to a plate. Cook remaining mushrooms. Arrange mushrooms over base of prepared cake tin. Top with tarragon and cooked leek.
3 Cut pastry sheets into 23cm circles. Put 1 sheet of pastry over mushroom mixture. Top with second sheet of pastry. Fold excess pastry around edge of tart towards centre. Brush with egg. Bake tart for 15–20 minutes or until pastry has risen and is golden and crisp. Stand for 5 minutes.
4 Meanwhile, to make mustard crème, combine crème fraîche, mustard, salt and pepper in a small bowl.
5 Put a large plate over cake tin and turn tart out (upside down). Serve with mustard crème.