Preheat the oven to 350℉. Line two baking sheets with parchment paper or silpat mats.
In a large bowl, use an electric mixer to combine the butter, cream cheese, sugar and salt. Beat until smooth and fluffy- 3 to 4 minutes. Add the eggs and vanilla extract and mix for another minute. In a medium bowl, whisk together the flour and baking powder. Slowly add the flour to the wet ingredients and mix just until it’s all incorporated. Cover the bowl with plastic wrap and refrigerate until the dough is firm.
Use a cookie scoop to measure an even scoop of dough (1 ½ to 2 tablespoons). Roll the blob of dough into a ball. Place it onto the baking sheet, and use the bottom of a glass that has been dipped in water and sugar to flatten it into a round cookie shape. Repeat with the remaining dough. sheet (space about 2-inches apart).
Bake 12 to 14 minutes until the cookies are no longer looking raw in the middle. Let them cool completely on the pan before transferring them to a rack.
MAKE THE FROSTING:
In a large bowl, use an electric mixer to cream the butter. Then mix in the vanilla. Add the powdered sugar and mix to combine. Mix in 1 tablespoon of cream, and then another. The consistency at this point might be what you are looking for (a nice, spreadable consistency), or you may need a little more powdered sugar or a little more cream.
Frost the cookies leaving a visible rim around the edge of the cookie, and add sprinkles on top. Lofthouse cookies should be refrigerated in a covered container.