Preheat oven to 350 degrees.
Prepare baking sheets. Either line 2 baking sheets with parchment paper (reccomended) or grease 2 baking sheets well with butter or oil.
Cream together butter, sugar and cream cheese until well-blended. It should have a light, airy consistency.
Add egg, lemon zest and lemon juice.
Using a fork, blend together flour, poppy seeds, and baking powder in a separate bowl and set aside.
Combine flour mixture with wet ingredients.
Using a large spoon, drop cookies on the baking sheets in 1.5-inch clumps. It should make about 18 cookies. Flatten each cookie with the back of a spatula or wooden spoon.
Bake for 10-15 minutes. The cookies should be brown at the edges.
Meanwhile, to make the icing, combine all the icing ingredients EXCEPT the remaining poppy seeds in a small bowl.
ALLOW COOKIES TO COOL COMPLETELY before icing. Ice them lightly, then garnish with poppy seeds and (if desired) more lemon zest.
