In advance: Make 1/4 in. puddle dots using thinned royal icing and tip 4. When dry, brush with white Pearl Dust. (Number of puddle dots needed will vary with each letter.)
Prepare and roll out dough. Cut letter cookies; bake and cool.
Outline letters with tip 2 and full-strength royal icing. Flow in centers using thinned royal icing in a cut parchment bag. Let dry 48 hours. Attach puddle dots with dots of icing.