Ischler are double-decker cookies of a size that should not be underestimated, at least when making them like the original, with a chocolate cream-filling.
My preparation for them is simplified a bit (and it still takes quite some time to make them), and I find them one of the best kinds of cookies to experiment a bit with the filling.
Thus, I make Ischler in a classical chocolate cream-filled version, glazed with dark chocolate.
Or, as Devil-Ischler, with a filling that incorporates chile pepper. Though frankly, I usually use chile ancho, making them with a pepper that is sweet and only slightly spicy, not really devilish.
But, if anyone leans that way, you can always put habanero pepper powder into the filling…
As Japan-Ischler I changed them a bit more, following the trend towards matcha (which has been a staple, not a trend, in this household). For that, I make the filling with white chocolate and matcha and glaze the cookies with white chocolate, as well.
Just be careful with Ischler. They are mighty tasty – and basically each one a small meal!