• Heat the oven to 350 degrees. Mix the first 7 ingredients in a large bowl on low speed. The lemon zest and juice really make this cookie dough smell and taste so good. Wrap the cookie dough in plastic wrap and place it in the refrigerator for at least an hour.
• Select a cookie cutter or two that are about 3 inches. You want your cookies to be fairly small since they have two layers. I used a Christmas tree cut out and one that resembles a flower. You will also need a thimble or a small cap from a jar to cut the center hole on each cookie top. I used the cap to my vanilla extract bottle.
• Dust the counter with flour and place half of your cookie dough in the center. Sprinkle the top of the dough with more flour and then dust the rolling pin with flour and roll the dough to 1/4 inch thickness. Cut 15-20 cookies of all the same shape. Using a spatula, put the cookies on an ungreased cookie sheet. Bake for 10 minutes. These cookies will be the bottom of your double cookies.
• While the cookies are baking, gather the scraps and the rest of the dough, dust the counter, and roll the dough out again. Cut the same number of cookies from the dough. This time use a thimble or small cap to cut the center out of each cookie. Using a spatula, place the cookies on a second cookie sheet. Next, decorate the cookie tops before baking.
  
• Beat the reserved egg whites in a small bowl until they are foamy. Put the finely chopped nuts and red sugar in a small bowl. Using a brush, dab a bit of egg whites on the cookie tops.
• Do not use too much egg white on each cookie, as it makes the cookies stick to the baking pan. Sprinkle each cookie with the chopped nuts and red sugar mixture. These cookies will be the top of your double cookies.
• Remove the first sheet of cookies from the oven and allow them to cool completely on a wire rack.
• Bake the cookie tops for about 8-9 minutes, checking them often. When done, remove from the oven and allow to cool on a wire rack. They will cook a bit more quickly than the cookie bottoms.
• Repeat this process until the dough is gone. Make sure to have the same number of tops AND bottoms of your cookies, so they match up later.

How to assemble the cookies?

• Once your cookies are cooled, place the bottoms on one plate and the tops on another plate. This makes it easiest for assembling the cookies.
• Select the jars of jam you will use. I always use seedless raspberry. I also used strawberry and grape. Orange marmalade is another good option. Place a small amount of jam in the center of the bottom cookie.
  
• Stack a cookie top on the jam and press down slightly. Place the finished cookies on a tray or in an airtight container for serving later. This recipe makes about 2 1/2-3 dozen double sugar cookies.