Combine the three flours and salt in a medium bowl; whisk to combine.

In a large bowl of an electric mixer, beat butter on medium speed until creamy. Add brown and granulated sugars and vanilla; beat until smooth, lighter in color and fluffy. Add dry ingredients; mix on low speed until well-blended.

Form dough into two disks; wrap in plastic wrap and chill at least 45 minutes or up to one week.

Heat oven to 350º F.

On a lightly floured surface, roll out dough to 1/4-inch thickness. Using cookie cutters dipped in flour, cut out cookies; place on a large cookie sheet(s) lined with parchment paper. Chill 10 minutes before baking.

Bake chilled cookies 10 to 12 minutes or until edges of the cookies begin to brown very slightly. The centers should remain light in color. Place cookie sheets on wire racks; cool completely.

For the Frosting: In a small bowl, whisk 2 tablespoons cream into powdered sugar until sugar dissolves and thickens. Continue adding cream 1 teaspoon at a time to achieve desired spreading consistency.

Frost cookies and add sprinkles if desired.