First the minced meat is fried together with the finely chopped onion. Meanwhile, the whole thing is seasoned with a pinch of salt and pepper. If the minced meat is nice and crispy brown, I add the creamed spinach (the minis can go frozen in the pan, if I only have a block of creamed spinach, I defrost it beforehand). Bring the whole thing to the boil briefly. If the sauce is too dry, add a little milk.
Now I season with a tablespoon of cream horseradish (if you like it spicier, you can also use normal table horseradish), a tablespoon of medium-hot mustard and a little nutmeg. Then I stir in a mug of crème fraiche (or sour cream) and let everything simmer a little longer. Meanwhile, cook the spaghetti in plenty of salted water and serve with the sauce.
It may well be that at the end you have to season a bit more with salt, because in my experience the spinach always swallows a bit of the seasoning.