Make sombrero brim: Mix 3/4 pk. of fondant with 2 teaspoons of Gum-Tex; tint light yellow and add ivory to achieve a straw color. Roll out 1/4 in. thick. Using knife, cut an 8 in. circle; reserve excess fondant. Position fondant circle inside cornstarch-dusted mixing bowl. Immediately imprint fondant with narrow end of tip 48, placing imprints close together in vertical and horizontal rows. Let dry.
Prepare and cover Mini Wonder Mold cake with reserved straw-colored fondant; smooth. Immediately imprint with tip 48 as for brim.
Tint remaining white fondant red; roll out 1/8 in. thick. Cut 15 in. long x 3/4 inch wide hatband; attach around cake with damp brush. Position cake on brim.