Separate eggs and place yolks in a large mixing bowl and the whites in another shallow bowl.
Cream together butter, sugar, vanilla, and salt with the egg yolks.
Gradually stir in the flour.
Using a small cookie scoop or teaspoon make 1-inch balls of cookie dough.
Roll dough balls first in the egg whites.
Then roll in the walnuts.
Place on a baking sheet and bake in a preheated 350-degree oven for 5 minutes.
Remove and using your thumb make an indentation in the center of each dough then return to the oven for 7-10 more minutes.
Remove baking sheets from the oven and let cool on a wire rack.
Make the icing by combining all ingredients and adding enough milk to give you a smooth, workable consistency. Keep some of the icing white and portion out the rest for as many colors as you'd like and add food coloring.
Spoon some icing into each cookie indentation.
Makes approx. 3 dozen cookies
Notes
Similar to shortbread cookies, the thumbprint cookies keeps well for a few of weeks in the freezer packed in an airtight container. Thaw at room temperature before serving.If you are not a fan of nuts you could try rolling the dough balls in sprinkles.
Nutritional information is provided as a courtesy and is an estimate only. This information comes from online calculators. Although attempts have been made to provide accurate nutritional information, these figures are only estimates.