Preheat oven to 350 degrees F.

In a medium mixing bowl, beat butter, sugar and vanilla with a hand mixer until smooth. Stir in flour, cornmeal and lemon zest and beat until dough clings together. Divide dough into 3 equal portions and roll into ropes about 1-inch thick. Place on a baking sheet lined with parchment paper. Flatten ropes slightly and press the back of a 1/4-inch teaspoon measuring spoon, or your finger to make a 1/2-inch wide indentation for every inch of the rope. Spoon a 1/4 teaspoon of jam into each indentation. Bake in oven for 10 to 14 minutes, until sides just start to brown. Let cool on baking sheet for 5 to 10 minutes. Place chopped white chocolate in a baggy in warm water. Push the chocolate into the corner of the baggy until thoroughly melted. Wipe off any water on the outside of the bag and snip the corner to drizzle chocolate over cookie ropes. Chill until chocolate has set and with a sharp knife cut ropes diagonally into 1-inch wide pieces. Store the cookies in an airtight container, separating the layers with waxed paper.