Leek and Goat Cheese Tart

I was inspired to make this tart from Huey (from Huey's Cooking Adventures).  You can use just leeks but I chose to use a combination of onion and leek.

Leek and Goat Cheese Tarts
Ingredients
 - 1 large leek
 - 1/2 onion
 - 1 sheet of frozen puff pastry
 - soft goat cheese (preferably with a rind)
 - pepper and salt
 - 1 egg yolk
 - 1tsp milk
 - 15g butter


Method
1.  Preheat oven to 180C.  Slice onion finely.  Slice leek in half, wash well and slice finely.
2.  Melt butter in a pan on medium-low heat and add the leeks and onions.  As you are sauteing rather than frying, use a low heat and stir.  Saute until the onions and leeks are translucent.  Add a lot of pepper and season with salt.  Take off the heat
3.  Cut the puff pastry into quarters.  Spoon the leek mixture into the middle of each pastry and flatten it down.  Add a few slices of goat cheese on top of the leek mixture.
4.  Lightly beat the egg yolk and milk and use it to generously coat the outside of the pastries. (see photo)

5.  Place into oven for 15-20 minutes or until the pastry has turned golden and puffy.  Serve.