Preheat oven to 350°F. Line a baking sheet with parchment paper. Set aside.
In a large mixing bowl, combine butter and sugar for the cookie dough. Beat at medium speed until well blended. Add in eggs, corn syrup, yogurt, lemon zest, and lemon extract. Beat until combined.
Beat in flour, baking powder, and poppy seeds. Using a 2 Tbsp cookie scoop, drop tablespoons of dough onto parchment paper lined baking sheets.
Bake for 10-12 minutes, just until the edges and bottoms begin to brown. Remove from oven and cool completely on wire rack.
To make the filling for the whoopie pies, beat butter for 2-3 minutes until pale in color. Add in powdered sugar, lemon zest and lemon juice. Beat for an additional 2-3 minutes until smooth and fluffy.
Using a plastic resealable bag, add filling. Snip off corner and pipe onto cookie. Add second cookie to make whoopie pie.
If desired, drizzle with melted white chocolate and yellow sanding sugar. ENJOY.
Notes
Don’t overbakethese cookies. You want to bake them just until the bottom edges begin to brown. For my oven it was 10 minutes, so keep an eye on them!
To add a little flair to your whoopie pies, drizzle some melted white chocolate over the tops. I spoon my chocolate into a resealable plastic sandwich bag and snip off the corner. Makes for an easy drizzle technique. Add some yellow sanding sugar sprinkles for that pop of yellow color!
The resealable sandwich bag trick works for piping the filling onto the cookies, too. Or you can use a frosting bag for this step, if you have one.
Want a less lemony filling? Swap the lemon juice for heavy cream instead.