Using either a (food processor, stand up mixer or by hand) add the flour and salt to the bowl, make a well in the flour and add the egg and yolk, lightly mix (pulse, with a fork or beat just to wet the flour), add the sugar and mix, then add the chopped butter and mix to form a smooth compact dough, wrap in plastic and refrigerate for an hour.
Remove the dough from the fridge and knead a few times to soften up the dough. Using a small round cutter (1.5 inches / 4 cm) or glass, form the cookies slightly thicker than pie dough (1/8 inch see photo). Leave half the cutouts whole and the other half cut out a small form in the middle (heart, round shape, star etc*).
Pre-heat oven to 350F (180C). Line 2-3 cookie sheets with parchment paper.
Place cut out circles whole and cutouts on prepared cookie sheets* and refrigerate approximately 15-20 minutes while the oven is heating.
Bake for approximately 10-15 minutes or until very lightly golden. Let cool completely. Place 1 teaspoon more or less of desired filling on the whole cookie and cover with the cut out cookie. Dust the the cookies with icing sugar if desired before serving. Enjoy!
*Be sure to bake the small cut out forms on a separate cookie sheet because they only take about 5-6 minutes to bake.
Notes
Baked cookies should be stored in an airtight container for up to 5 days, or they can also be frozen in an airtight container for up to three months.You can also freeze the unbaked cookie dough wrapped tightly in plastic then placed in an airtight freezer bag for up to three months.