1. Prepare the cookie dough. In a large mixing bowl, sift together the flour, powdered sugar and salt. Set aside.
2. In the bowl of a stand mixer fitted with the paddle attachment or with a handheld mixer, combine the cream cheese with the butter on high speed for about 2 minutes, or until smooth and creamy. Add the egg, lemon juice, lemon and vanilla extract and mix until combined. With the mixer running on low, slowly add the dry ingredients and mix until just combined. Cover the dough and chill for at least 2 hours, or up to 2 days.
3. Bake the cookies. Preheat the oven to 325 F and line two large baking sheets with parchment paper. Remove the cookie dough from the fridge. If it’s been chilling for more than a few hours, allow it to come to room temperature for about 20 minutes first. Using a medium cookie scoop (1.5 tbsp) place the cookie dough balls a few inches apart. Press down lightly with the back of a spoon to flatten the balls a bit. Bake the cookies for 8-10 minutes. When you remove the cookies from the oven, they will look puffy and slightly undercooked. Let the cookies rest for 5 minutes on the baking sheet before removing them to a wire rack to cool completely.
4. Prepare the icing. In the bowl of a stand mixer fitted with the paddle attachment or using a handheld mixer, combine the cream cheese and butter. Mix on high speed for about 2 minutes, or until smooth and creamy. With the mixer running on low, add the powdered sugar and the cream, followed by the lemon extract and lemon zest. The icing should be fairly thick but spreadable. Add either more powdered sugar or cream to reach the desired consistency. Spread about 2 tsp icing on each cookie, followed by sprinkles!

Cookies will keep at room temperature, in an airtight container, for 2-3 days, or up to 1 week in the refrigerator. You can also freeze un-iced cookies for up to 2 months.