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.
3. Add the egg yolks and vanilla and mix on medium speed until well combined.
4. Measure in the flour and mix until large crumbles form. Add in the milk and mix well. The dough should NOT form a ball. It should be sticky and have the consistency of very thick buttercream. If you stick your spatula in the dough and pull it out, some of the batter should stick - that's perfect! If you're dough is not sticking enough after adding all of the milk, you can add a bit more but avoid using too much as this can cause the cookies to spread and lose their shape.
5. Transfer the dough to a extra large, heavy duty piping bag fitted with a large open star tip.
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.
   To make star cookies, hold the piping bag vertically and squeeze until your star shape is about 1 inch in diameter.
7. *For star cookies, before baking, decorate with sprinkles if desired. Or, if you plan on filling them with chocolate, use a ¼ teaspoon that is floured to create a divot or well in the center of the cookie.
8. Bake cookies in the oven until light golden brown on the edges, about 10 - 13 minutes.
9. Transfer to a baking rack to cool completely, you can also allow to fully cool on baking sheet.

To Make Sandwiches

1. Melt the chocolate in the microwave in 15 second intervals (stirring well in between each) until fully melted and smooth.
2. For sandwiches, spread a little less than ¼ tsp of jam or ganache onto one side of the cookie. Sandwich together.
3. 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.

To Make the Ganache (can be used for sandwich cookies or as the center of the star cookies)

1. In a large glass bowl, microwave the cream for about 30 seconds or until hot and almost simmering.
2. Add in the chopped chocolate/chocolate chips. Allow the chocolate to sit in the cream for 3-4 minutes.
3. Once the mixture had time to rest, stir the cream and chocolate together. The chocolate should be melted into the cream but feel free to pop the bowl back in the microwave for a few more seconds if needed.
4. Allow the ganache to cool back down for a few minutes.
5. Spread between the sandwiches or pipe the ganache into the wells of the star cookies.
6. It's best for these to set in the fridge to firm up.