Lightly spoon flour into a dry measuring cup. Combine flour and next 4 ingredients, stirring with a whisk.
Place sugar and butter in a medium bowl and beat with a mixer at medium speed 2 minutes or until creamy. Add molasses and beat until smooth. Add egg yolk and beat until well combined. Add flour mixture to sugar mixture, stirring until well combined.
Shape dough into 24 balls, about 1 ½ teaspoons each. Place 2 inches apart on 2 parchment-lined baking sheets. Flatten balls to ½” thickness with bottom of a glass.
Bake each batch for 10 minutes. Cool on pan 4 minutes on wire rack, then remove from pan. Cool completely.