How can you keep a stack of Swedish pancakes fresh?

You have this same problem with most fried foods that you want to serve fresh. Anyone who makes latkes for Hanukkah knows this problem well. So it's similar to this question What technique should I use to make latkes for a party so that I don't have to stay in the kitchen?

You can try what I do for latkes - I put them on a drying rack, sheet pan, skillet, etc. in the oven set at around 250°F. You may want a lower temp for Swedish pancakes, like 200, since they are less dense. They will not be the same as fresh from the frying pan, but they will stay warm and crisp.

For reheating, put them in a dry cast iron or non-stick skillet or in the toaster oven on 375-400 for 4-5 min, more or less time depending on thickness and initial temperature.

If you do this a lot you could also invest in a heat lamp/warmer set up like they use at fast food chains to keep the fries warm. Cheap one on Amazon - http://www.amazon.com/Home-HL100SV-Culinary-Heat-Lamp/dp/B0043M5N08

Many a Top Chef participant has been felled by this problem though - fried foods, blinis, etc. are never the same as when taken out of the fryer fresh, but they are still quite good out of the warm oven.

For American pancakes, my mom would always warm a plate or two in the oven, and then stash them in there as they were done cooking ... but American pancakes don't suffer as much from losing a crispy edge, and you'd run the risk of them steaming. You might be able to counter this somewhat by a clean towel in between them.

When I do dutch pannekoeken, which are really similar to swedish pannkakor (which I assume is what you mean by 'swedish pancake' and not plättar, as you mention 'stack'), I find that they keep their texture better if I roll them up as I make them, and then put the rolls on the plate in the oven. This results in more surface area exposed in the oven, and they won't steam quite as quickly.

The only other suggestion I have is that if you're not already -- cook two at a time. It requires getting the temperature dialed in correctly on both pans, but you basically coat one pan, then the other, wait about 30 seconds (depends on how dark you like 'em), flip the first, count to about 15, flip the second. (It might be possible for some people to do three at a time, but I only have two pans that are appropriate, and I wouldn't be able to fit a third pan that size on my stove) This might not work if you've got something else on the stovetop at the same time, but if it's pea soup, you could get that done earlier, and move it to the oven to keep warm.

The other way is to make ungspannkakor, which you cook in a non-stick deep baking tray in an oven at 180, that way everyone gets to sit at the table and eat together. this is also delish reheated in a non-stick fry pan so you cook it in advance, reheat it and serve in in a spectacular pile in the middle of the table. for this you use the same recipe as you would for pannkakor.