Pirozhki with potatoes and wild mushrooms

Pirozhki - individual pies - are a staple of the Russian cuisine, there are so many variations and methods of preparing them, that one would need to write a mini-encyclopedia just on the topic. They can be fried or baked, sweet or savoury, made with meat or vegetarian. My Mum's pirozhki are of course the tastiest in the world.
Just the other day I was singing praises to the wild mushrooms from Tesco (see my post Girolle and garlic pasta). I saved the 2nd pack for Pirozhki with potatoes and wild mushrooms. Mushrooms and potatoes are a classic combination, and they complement each other beautifully.
For a budget recipe, skip the mushrooms altogether and just do the filling with the mashed potatoes and fried onions. When I was a student, that was often the option for a cheap tasty meal.

Pirozhki with potatoes and wild mushrooms (makes 20)
Ingredients:
100g wild mushrooms (girolle or ceps)
150g potato
2tsp butter
1 small onion
salt, pepper
1 pack of Jus-Rol shortcrust pastry
1 egg yolk

I know the likes of Paul Hollywood and the GBO contestants would pooh-pooh me for using the ready-made pastry, but I am not ashamed to admit that I use it. Jus-Rol makes pretty good pastry, and it is very convenient for busy Mums like me.

Start by peeling the potato and cooking it in the salted water until just soft. Mash it with a fork and add 1tsp of butter and a bit of the liquid in which potatoes were cooking or a dash of milk. Don't make it too runny.
Brush the specks of dirt from the wild mushrooms - I used the beautiful girolles from Tesco - and chop them with a knife. In a small frying pan melt 1tsp of butter, add the finely chopped onion and fry for about 5 minutes, then add the mushrooms and fry for another 5 minutes, stirring occasionally.
Mix the mashed potatoes and mushrooms. This is your filling for the mini pies.

Now roll out your pastry, and using a cookie cutter, cut the little circles. You will have some leftovers, knead them together in a ball, and reroll the flattened dough. Cut more circles. Slightly stretching each circle of pastry, add a teaspoon of the filling, fold the edges, so that they meet like a little purse, and pinch them together. Place all your pirozhki on a big baking tray, which has been oiled. Beat the yolk with a fork, and using your fingers or a pastry brush, brush the yolk over pirozhki. You could also use a bit of milk for the same purpose or melted butter.
Put the tray in the oven preheated to 180C and bake the pirozhki for about 20 minutes until golden.
Serve with the pickles and a generous dollop of the soured cream. They are also often accompanied by a hot steaming mug of clear broth or bouillon.
They are tasty both hot and cold.
Na zdorovie! Enjoy your meal!

I'm participating in the 1st Edition Tiendeo cooking competion "Seasonal Recipes".