What can I do to make my Cheese & Onion Pie freeze well? Here is my Mum's recipe for what she called Cheese &amp; Onion Pie, which was a favourite of mine as a child, and I continue to make occasionally to this day. 


Boil some chopped potatoes until soft. 
Drain, add milk and butter, and mash them. 
Add grated cheese and finely chopped red onion and mix. About two thirds potato, one third cheese &amp; onion. 
Transfer it into a dish.
Cover with pastry (I cheat and use ready made pastry, sorry)
Bake in the oven for about 35 minutes.


This works very well. Over the years I've experimented with different types of cheese, and also things like black pepper and garlic.  

However, if I freeze it, it does not defrost very well. It comes out watery and with a lot less taste. 

I have tried leaving it to defrost at room temperature, defrosting it quickly in the microwave, and putting it straight in the oven frozen. The end result is the same. 

I have also tried leaving the pastry out and just freezing the mixture. 

There are two issues with freezing it:-  The watery texture, and the taste. Are they connected? 

Is there anything I can do to make it suitable for freezing?

To clarify: I make a large pie, serve half and freeze the other half. I'm not making it specifically just to put in the freezer.
The way to freeze this well would be to use instant potatoes simply mixed cold and not cooked.  Then when you bring it out to reheat, you'll cook the potatoes.  The taste will be of instant potatoes, though.

The problem is that the starches in the potato will undergo retrogradation, recrystallize and expel moisture when reheated.

You could counteract this by stirring in some potato starch after the potatoes have cooked and cooled and before you assemble the pie, but the instant potato method will work better and will require less experimenting.