Bubble and squeek works much better with leftover roast potatoes rather than mash, less sludgy when you've finished. If i wanted to make it into a muffin shape I would cook it first in the pan then stir the browned bits in and then preheat a metal muffin pan with a little bit of fat in each cup, drop in the mixture quicky and then put in a very hot oven for only a few minutes, so the outside of the muffin would get nice and crispy and brown. Then it would hold shape and could be frozen and reheated. the only possible issue I can see is if the mash/potatoes have to much moisture in them they may weep when defrosted and fall apart.
What do you want these things for? Is it breakfast, as a side dish for dinner or a quick lunch?
Hash browns would work if you didn't make them to deep in the tins, only needs potato and onion I use a bit of flour as a binder.
Stuffed cabbage cups. line the moulds with a cabbage leaf, fill it with a flavoured rice mix and fold the leaf over the top, reheat upside down so it holds together.
Same as the above but with a tortilla as the liner would probably reheat better.
Tiny little pies! Use a thin pastry lining fill with any veg/beans of your choice bake and freeze.
Samosa muffin.. line the tin with filo pastry and fill with potatoes/onions/peas. lots of recipes for samosas online so just make that mix but bake it in a muffin rather than frying it.
Stuffing muffins and savory bread puddings! I've done both, and though I haven't tried freezing any ahead, I'm sure it would work. Maybe make them a little moister than you might normally want them, to make up for freezing and reheating.
Since my hubby started baking bread, savory bread puddings have become a staple around here. I'm partial to using mushroom and whatever fresh herbs and leftover cheese we have.
She's got lots of breakfasty ones like banana, pumpkin oat, cranberry apple. But lots of savoury ones too - turmeric rice, quinoa kale, red lentil.
I know you said easy to get ingredients, and she does use a lot of chickpea flour. Don't let that turn you off until you look around. The towns in my area are less than 8000 people and I can find it in all of them. The walmart in the closest (and smallest of the three towns nearby) has three different brands of chickpea flour, so you might be surprised at its availability.
It uses mash potatoes. there is a video of the flipping it over. I don't think I would ever master that technique.
I am also thinking about boiled cubed potatoes with a white sauce. I have Corningware French White individual casserole dishes I could freeze the potatoes in the dishes. Then empty the dish when frozen and then when ready to cook put them back in the dish.
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