Preheat oven to 350F. Line 2 baking sheets with parchment paper and set aside.

In a large bowl beat butter until light and fluffy. Add in icing sugar and mix until smooth. Beat in vanilla.

In a separate bowl whisk flour, cornstarch and salt together. Stir into the butter mixture in 3 additions to form a soft dough.

Roll out dough into 1 inch balls. Place on cookie sheet and lightly press down a bit with your hand to flatten. Bake for 12 minutes, or until lightly golden. Cool completely on cookie sheet.

Combine raspberries and sugar in a small bowl and mash them with a fork. Let sit for 15 minutes. The raspberries will slowly release their juices.

Push berries through a fine sieve to extract all the juices. Discard the solids.

Combine raspberry juice and powdered sugar in a small bowl. Add in milk slowly until icing becomes the right consistency to sit on top of cookie and will not drizzle off.

Taking 1 cookie at a time, dip top into the icing and allow the excess icing to drip off. Place cookie upright on baking sheet and add sprinkles. Continue with all cookies.

Allow icing on cookies to dry and then store in an airtight container. Cookies will keep for 1 week.