Preheat oven to 350°F.

To prepare the crust, cut the butter into small pieces. It doesn't have to be cold, but you don't want it too warm so it's melting.

Add the flour, salt and sugar to the butter and rub by hand to combine.

Switch to a spoon and add the milk in a thin stream, mixing until it just holds together.

You may not need all the milk.

Firm into a disc, cover in plastic wrap and chill while making the filling.

Sprinkle surface and top of dough with flour, roll gently from the center to the edges until it's large enough, turning it over a few times so it doesn't stick.

Lift gently into the pan, and crimp edges as desired.

Prick the crust all over with a fork and bake for 10 to 15 minutes or until lightly browned.

For the filling, fry the bacon over medium heat until done.

Remove the bacon from the pan, reserving about 2 tablespoons of the drippings.

Cook the onions in the bacon drippings until nicely browned, stirring often.

Drain off the drippings.

In a large bowl, combine the bacon, onions, egg, egg yolk, sour cream, salt, pepper, chives (or shallots) and caraway seeds (if using).

Mix well and pour into the crust

Bake until the filling is firm and golden, about 35 to 40 minutes.

Serve warm.