LIME SANDWICH COOKIES

Steps:

• Whisk together flour, baking powder, and 1 teaspoon salt. Beat 2 sticks butter with sugar on high until fluffy, 4 minutes. Beat in egg, vanilla, and 1 tablespoon water. Reduce speed to low; add flour mixture and beat to combine. Divide dough in half; flatten into disks. Wrap in plastic and freeze until firm, 30 minutes.
• Preheat oven to 325 degrees. Remove one disk from freezer; let stand 15 minutes. On a floured surface, roll out 1/8 inch thick. Using a 2 1/2-inch cutter, stamp out rounds; place on parchment-lined baking sheets. Roll scraps; cut out more rounds. Repeat with other disk. Cut 3/4-inch teardrops from half of cookies. Refrigerate 30 minutes. Bake, rotating sheets once, until edges are golden, about 20 minutes. Let cool on sheets on wire racks.
• Heat milk in a small pan over medium-high, stirring until bubbling. Reduce heat to medium. Cook, stirring, until it has the consistency of pudding, 5 minutes. Strain into a bowl. Whisk in juice, zest, and a pinch of salt. Cover surface with plastic; refrigerate 30 minutes.
• Beat remaining 6 tablespoons butter, cream cheese, and milk mixture on medium-high until fluffy. Spread 2 teaspoons filling on a solid cookie; top with a cutout. Repeat with remaining cookies. Refrigerate, covered, at least 1 hour and up to 4 days.