Make chalkboard 2 days in advance. Knead 1 teaspoon Gum-Tex into 6 oz. of fondant. Tint half of the fondant ivory and half black. Use fondant roller with purple guide rings to roll out ivory and black fondant, separately, 1/8 in. thick. Use knife, black fondant and pattern to cut chalkboard. Use knife, ivory fondant and pattern to cut background. Place pieces on cornstarch-dusted cake board. Let dry, about 2 days.
Make layered cake. Prepare batter following recipe directions. Bake and cool two 8 in. cake layers. Prepare buttercream icing following recipe directions. Crown, torte, fill and stack layers for a 2-layer cake, 4 in. high on foil-wrapped cake board. Use spatula to ice cake.
Assemble chalkboard. Cut bright white Candy Melts candy wafers in half and place in refrigerator. Use leftover fondant to prepare thinned fondant adhesive following recipe directions. Use brush and thinned fondant adhesive to attach chalkboard to ivory background. Use candy wafer halves to write message on chalkboard. You may need to use a fresh chilled wafer for each letter.
Melt bright white candy melts candy in disposable decorating bag according to package directions. Use white melted candy and cut disposable decorating bag to attach lollipop stick to back of chalkboard. Chill until firm, about 3 to 5 minutes. Insert chalkboard into cake.