1. Preheat oven to 350 degrees and line cookie trays with parchment.
2. In a large bowl, cream the butter, sugar & salt until light and fluffy using a hand mixer or stand mixer.
3. Add the eggs on low speed, one at a time, until combined. Add vanilla extract, then mix on medium speed until well combined.
4. Slowly add the flour to the mixture and mix until a dough forms. Use a rubber spatula to scrape down the sides of the bowl. Mix until a semi-soft, sticky dough is formed. 
5. Transfer the dough to a heavy-duty piping bag with a large open star tip. I like to put my pastry bag with the tip in a tall glass and fold the open bag on the outside of the cup to hold the bag steady as I fill it with the dough. 
6. For sandwich cookies, pipe the dough into 2″ strips leaving 1 ½ inches between each cookie. Use a sharp knife to trim the edges to make a clean edge.
7. For circle cookies, hold the piping bag vertically and squeeze until your cirlce shape is about 1 inch in diameter. *For circle cookies WITH sprinkles* decorate with sprinkles BEFORE baking. You can also create a small hole with you index finger if you want to fill the cookies with chocolate or jam.
8. Refrigerate the piped cookie dough for about 30 minutes before baking. 
9. Bake cookies for 10-12 minutes or until they are light golden brown on the edges. Do not over-bake. 
10. Cool the cookies on the sheet for 5 minutes before transferring them to a cooling rack to cool completely. Dust with powdered sugar or assemble as desired. 

Assembly- Sandwich Cookies

1. For sandwiches, spread a little less than ¼ teaspoon of jam, Nutella, or other desired filling onto one side of the cookie. Sandwich together with another cookie.

Assembly- Dipped Cookies

1. Chocolate Ganache- Melt the chocolate in the microwave in a small microwave safe bowl 15 second intervals (stirring well in between each segment) until melted and smooth. If you want to make it glossy add a dab of butter and stir until combined.
2. Dip one end of the sandwich cookie in melted chocolate and lay on a rack. Add sprinkles and allow the chocolate to set at room temperature.