Lemon-Cream Sandwich Cookies

Yesterday was my friend's baby shower so I made these cookies to celebrate! Both the filling and cookie are lemon flavored:

Recipe from Bon Appetit magazine (Jan 2009)

Cookie:
1/2 cup fresh lemon juice
1 Tbsp lemon zest
3 3/4 cup flour
1 tsp salt ( I used 1/4)
1/2 tsp baking soda
2 sticks unsalted butter
1 1/2 cup sugar
2 eggs
2 egg yolks

Filling:
1 1/2 Tbsp lemon zest
dash salt
1 stick unsalted butter
2 cups powdered sugar

Cookies:
Boil lemon juice and zest in saucepan till reduced to 2 Tbsp. Let cool. Beat butter till fluffly, add sugar and mix well. Beat in eggs and yolks, one at a time. Add lemon juice. In another bowl, sift together dry ingredients. Then add the dry to the wet mixture and blend. Cover and chill dough till firm, at least 4 hours and up to 1 day.

Preheat oven to 375. Line 2 baking sheets with parchment paper. Roll out 1/3 dough to 3/8 thickness. Using 2 inch round cutter, cut out cookies. Bake 10-12 min. (I used a 1 inch round and made them thinner and ended up with almost 100, so you may need to adjust depending how many you want, and the size of your cutter). Repeat with remaining dough.

Filling:
Mash zest and salt into a paste. Add butter. Beat with electric mixer till fluffly. Add sugar in 4 batches, beating after each till blended.
(Can be made 1 day ahead. Cover and refrigerate. Bring to room temp before using).