Directions

1.  Combine butter, sugar and flour in a food processor and mix until thoroughly blended. It should look a bit grainy. Add the egg yolks one at a time, then mix only until dough comes together into a soft ball. If it doesn’t ball up, you may need more egg yolk.  
2.  Divide the dough into two pieces of equal size, pat into rectangle shapes and wrap individually in plastic wrap. Chill for at least an hour.
3.  Roll out dough between two pieces of parchment paper into rectangles of roughly equal size and shape. The dough will be somewhat sticky and soft.
4.  Preheat oven to 350°.
5.  Leave the rolled-out dough on the parchment paper and place on baking sheets. Bake for approximately 12-14 minutes, keeping an eye on them, as the dough is delicate and will brown very quickly!
6.  Keeping the pastry on the parchment, slide one onto your counter. Spread evenly with a generous layer of jam and then carefully slide the other pastry onto the top, fully covering the jam. Note — the pastries are very delicate. We had success using two extra large spatulas to move them. Don’t worry if the pastry cracks on top — the frosting will cover it.
7.  While they are cooling, make the frosting. Combine all ingredients in a bowl and mix well. The frosting should be easy to spread — you may need to add extra liquid (milk or water). You can also add a few drops of natural food coloring if you like and sprinkles when you’re done.
8.  Using a large sharp knife, cut into squares. Be sure to square off the outer edges too — the leftover ‘shnibbles’ are your treat for a job well done!