Here's a version I threw together last night that was quite good.
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Potluck Potato Kügel
Feel free to add and subtract things that make sense (ex. cooked or grated carrots).
This will probably work with up to a cup of leftover mashed potatoes. I had about 2/3 cup.
Add about 1 tbs. each chopped green pepper, celery and onion. 1 minced garlic clove. Salt and pepper to taste. (I used white pepper.)
2 jumbo eggs.
A little (1-2 tbs.) matzo meal, cracker meal or breadcrumbs.
A dash of turmeric (for health and color.) A dash of smoked paprika (can't hurt!)
1 tbs. rendered chicken fat or olive oil if you're not into the schmaltz.
Mix well with a fork. Pour into a greased oven-proof dish (I used a Pyrex bowl). Allow room for it to rise about 50%.
Bake in a tabletop convection oven (a/k/a glorified toaster oven) at 425° for approx. 25 minutes until golden (not burnt) brown.
Allow to cool slightly before serving.
Probably works in a conventional oven, too. Lemme know.