What can I use frozen spinach for that is reasonably healty (i.e...

What can I use frozen spinach for that is reasonably healty (i.e. doesn't involve adding a shitload of butter and cheese)?

I got a zero calorie recipe for you. Let it mostly thaw, mold it into a dick, refreeze, and then shove it in your asshole.

Just throw it in a pan with a little diluted apple cider vinegar or malt vinegar and a lemon wedge and eat it with some fish.

Try microwaving it a couple minutes, squeezing the water out if it with paper towels and then adding it to basically anything. For most people it is the slimy texture that is the turn off.

butter is healthy, unless by wanting something healthy you mean youre fat and cant afford the extra calories

just drop the cheese, pan frying with butter+garlic is fine

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A traditional meal in our family is boiled spinach (with just some salt, pepper, nutmeg and maybe a dollop of cream) served alongside some boiled potatoes and eggs fried sunny side up. Goes together very well.

That really depends on what you consider a shitload of butter, really. Howsabout eggs in spinach sauce? That uses either butter or olive oil, about 1tbsp per serving.
To make it, thaw the spinach and wring it out then chop finely and set into a pan with thinly sliced onion and minced garlic.
Add butter/oil, salt generously and set to high heat.
When fragrant, saute about until the garlic begins to colour then add a bit of unsalted veg stock to just cover.
Let it reduce out again and saute some more, watching for the garlic to begin browning.
Add a bit more veg stock and repeat, watching for the garlic/onion to start caramelising.
Add another bit of veg stock and, once again, reduce back out, watching for the onion to soften and darken considerably.
Finally, add the last bit of stock, blitz the lot smooth and adjust seasoning to taste.
Crack in a few very fresh eggs and poach to bull's eye doneness. The albumen of older eggs tend to spread and turn the whole thing into one solid coagulated mass. It'll still taste good, but the point of the dish is to have eggs in a sauce, kinda like shakshuka.
Serve up the eggs first then add a little cooking cream to the spinach sauce (the stuff is thick like sour cream, but not remotely tangy; if you can't find it in your country, add sour cream instead or just omit wholesale).
Add a spoonful of sauce to each plating of egg and serve up with a good, crusty bread.

Option 2 is simply to saute in garlic scented olive oil and eat as a side dish. To scent the oil, put some of it into a cold pan with a few thinly sliced cloves of garlic.
Set to high heat and, when fragrant, turn it off again. The oil is now scented. Best to use it quick.

I do this nearly every Thursday night, pairs lovely with with a merlot or an amyl nitrate.

Fisherman's eggs