Preheat the oven to 350 and line a baking sheet with parchment paper.

In a medium bowl whisk flour, and salt, mix until well incorporated.

In a large bowl using an electric mixer or the bowl of a stand mixer fitted with a paddle attachment cream butter and sugar until well incorporated.

Add in egg yolk and vanilla and continue mixing on medium speed until well mixed.

Add the dry ingredients in gradually, mixing after each addition, until it is all added.

Scoop out cookie dough in tablespoon size scoops and roll into balls.

Place on the prepared cookie sheet.

Using the handle of a wooden spoon, your finger, or another small round object press a hole in the center of each dough ball.

Bake cookies for 10 minutes.

Remove from the oven, gently press in the center of each cookie again.

Place back in the oven and bake 8-10 minutes or until the cookie is light golden brown.

Allow to cool on the baking sheet for 2-3 minutes before removing to a wire rack to cool completely .

In a medium bowl combine powdered sugar, corn syrup, vanilla and 2 tsp milk. Mix until well incorporated. If the filling is too thick add additional milk ½ tsp at a time. You want it thin enough to scoop out but thick enough to set and not run out of the cookies. Add in the green food coloring a little at a time until the desired shade of green color is reached.

Fill each cooled cookie with the filling, you can place the frosting in a piping bag and pipe it into the cookies or use a spoon and spoon it into the center of each cookie.

Immediately place a heart shaped sprinkle in the center of each cookie

Allow the cookies to sit uncovered until the filling has set.

Store in an airtight container.