Preheat oven to 325.  Line cookie sheet with parchment paper or nonstick liner.

Whip butter and sugar together for a few minutes until thoroughly mixed.  You may need to stop and scrape sides of bowl halfway through. 

Mix in vanilla and salt.  On low mix in flour a little bit at a time.  

Dough will come out sticky, roll into a ball and wrap in plastic wrap thoroughly.  Put in the fridge to chill for 30-60 minutes.  If you leave it in longer you will need to let it sit out room temperature for 10-15 minutes before you can work with it. 

Flour the counter liberally to prevent the dough from sticking.  Roll out the dough using a floured rolling pin.  Once thickness is about 3/4 inch start cutting out your mouse shapes.  

Using a spatula carefully pick up each cookie and gently press your thumb into the head and ears areas.  once it is deep enough without piercing through the bottom of the dough add the preserves of your choice into all three areas.  

Bake 18-25 minutes until slightly golden brown around the edges.  Time will depend on thickness of cookies. 

Let cool for 5 minutes then transfer to a baking rack.  Let cool an additional 10 minutes before serving.