Preheat the oven to 350°F.
Beat the butter, sugar and salt until smooth.
Beat in the egg yolks and vanilla extract.
On low speed slowly mix in the flour until just combined. Mix in the milk as needed.
Scoop two heaping tablespoons of the dough into a piping bag fitted with a large round tip. Set aside.
To the rest of the dough mix in the cocoa powder until combined. Transfer the dough to another piping bag fitted with a very large star tip. Do not over fill the bag as it will be difficult to pipe the cookies!
With the chocolate dough, pipe two little ears side by side onto a parchment lined baking pan. Then pipe a large round face making sure it is touching both ears. Continue with the rest of the dough, keeping the cookies about 2-3 inches apart.
With the vanilla dough, pipe a round snout in the centre of each face. At this point it is a good idea to chill the cookies in the fridge for 20-30 minutes. This will help keep their shape while baking.
Bake for about 12 minutes, or when the snouts are just slightly beginning to brown.
Let cool completely. With melted chocolate or icing, pipe the eyes and the nose on each bear!