They freeze quite well - I make a batch of them mashed (with butter, salt and some maple syrup), then used an ice cream scoop to dollop it out onto a lined baking tray. Once they've frozen you can bung them all in a bag together, and just microwave them from frozen when you want them. Not quite so healthy but very yummy!
You can use them in place of pumpkin in baking recipes so, muffins, cupcakes, cornbread (nice with chilli). Puréed sweet potato is also nice in oatmeal (top with butter and maple syrup and chopped nuts) or in American style pancakes.
I use them a lot to make African-peanut stew and red lentil and sweet potato chilli.
oven fries? -chop in thickish stick and toss in a drizzle of olive oil & a sprinkling of cinnamon + sweet parka + salt + pepper - roast in a single layer about 20-5mn they come out crispy and sticky outside, mushy inside.
a sort of "dauphinoise"? - Peel and chop - stir fry in a big pan with 1 white onion, add a bit of water to deglaze and season. - layer in ovenproof dish, cover with a little bit of thin white sauce, a little bit of single cream. - sprinkle with grated nutmed and grated cheese. Bake for 20mn
They make a delicious treat prepared as you would for candied apple. -slice and roast on a griddle pan - toss in a light toffee sauce( brown sugar and butter or single cream) - let them cool on a rack