Glittering Lemon Sandwich Cookies

I love lemon. Anything made with lemon is alright by me. Probably because it is almost always combined with something sweet :)

These little lemon sandwich cookies come out looking like mini Christmas tree bulbs. But much better to eat! You need to make the balls super small so when you make the sandwich they aren't unreasonable to eat. This year I'm going to try and make some of them like a thumbprint cookie, with the frosting on the inside, to make them a little more manageable. One other note - make sure all of the batter is well blended. If some has too much butter, they will spread and then you won't be able to make a sandwich out of them. Instead, you will just have to eat them - too bad!

For Cookies:
1 1/3 cups of all-purpose flour
2/3 cups of cornstarch
1/4 tsp salt
2 sticks unsalted butter, softened
1/2 cup confectioners sugar
1 tbsp grated lemon zest
1 tsp vanilla
Colored sanding sugars (I like blue, pink and yellow - you can find these at craft stores like Michael's or at specialty food stores, like Sur La Table, in their baking sections)
Equipment: parchment paper

For Filling
1 cup confectioners sugar
1 tbsp grated lemon zest
1 tbsp fresh lemon juice
2 tbsp light corn syrup
1/2 stick unsalted butter, softened
Equipment: a heavy-duty sealable bag

Make Cookies:
Preheat oven to 350F with rack in the middle. Line 2 large baking sheets with parchment paper.
Whisk together flour, cornstarch and salt.
Beat together butter and confectioners sugar with an electric mixer until pale and fluffy, then beat in zest and vanilla. At low speed, mix in flour just until a soft dough forms. Make sure it is well mixed, but not over mixed (so scrape the sides and let the mixer run for another 30 seconds or so)
Put sanding sugars in individual bowls. Roll a scant tsp of dough into a ball and drop into sugar, turning to coat. Reshape if necessary. Continue rolling balls and place on baking sheet about 1 inch apart. Once the first pan is full, put into the oven.
Bake until tops are slightly cracked but still pale - 12 to 15 minutes. Mine always take closer to 12 minutes.
Transfer cookies on parchment to a rack and cool completely. Form and bake additional cookies on the next sheet.
Will make about 100 total cookies, or 50 sandwich cookies.

**I tried to make a couple of these a little larger, and then pressed my index finger into the ball to create an indent. The indent will rise during baking, you will not have a deep depression.

***I've made the cookies a few days ahead, and then the day of or day before I've filled the cookies.

Make Filling:
Beat together all filling ingredients in a large bowl with an electric mixer at medium speed until combined well. Transfer to sealable bag to create a pastry bag - snip off 1/8 inch on the corner.
Turn over 1/2 of cookies and pipe about 1/2 tsp filling on flat side of each. Sandwich with remaining cookies, pressing gently.