Isler (Ischler) Jam-filled cookies glazed with choclate

I visit and browse No Salty on daily basis, to bookmark recipes that interest me. On 23rd , day before eve of christmas , I've done all my christmas baking but then I found this Isler cookies on the main page and couldn't resist this simple recipe.

I've no idea why the name "Isler" (correction : Ischler) . All I know is that its list of ingredients and that it is sandwiched with jam is very similar to the Linzer cookies. Also, whenever we buy Linzer cookies at the bakery we tend to add a few Isler (Ischler) to the mix.

Isler Cookies
source : No Salty

Ingredients

For cookies

280 g flour
280 g unsalted butter, soften
150 g ground nuts ( I used a mix of walnuts and almonds)
140 g powdered sugar
1 Tbsp rum
a pinch of salt
For the filling
Jam of your choice
Glaze
200 g chocolate
Method
1) Cream soften butter with powdered sugar. Do not over-mix. Incorporate flour, ground nuts, pinch of salt and rum into the butter-sugar mixture until the whole thing come together. Chill in fridge for 1 hour.
2) After an hour, roll out the pastry until the thickness of 3 mm. Use round cookie cutter to cut pastry. Cut until all pastry are used. Baked for 10-12 mins at 175°c
3) Let cookies cooled. Meanwhile, melt chocolate to get ready for assembly.
4) Sandwich cookies with jam and glazed with melted chocolate.
5) Store cookies in a tin can and place in a cool place at least overnight, to allow the flavour to develop.

Own Notes

1) I'll roll the pastry thicker next time. Mine was a bit too thin when baked, making it too fragile to handle.
2) For a more even finish of glazed chocolate , I shall coat the whole of top piece with chocolate next time by either pouring the melted chocolate over it or submerging into melted chocolate instead of spreading on top.