Preheat oven to 350 degree F. Line a baking sheet with a piece of parchment paper and set aside.
In a large bowl, whisk together flour, cornmeal, baking powder, salt, and chopped walnuts. Set aside.
In a medium mixing bowl, whisk eggs, maple syrup, and vanilla extract.
Make a well in the center of the flour mixture and pour the wet ingredients into well. Stir until the dry ingredients just come together. Turn dough out onto a lightly floured surface and knead until dough comes together. Divide dough into two pieces. Form each piece of biscotti dough into a 12" x 1½ long log shape and place on prepared baking sheet.
Bake in preheated oven for 25 minutes. Remove from the oven and let cool for 15 minutes. Turn oven temperature down to 325.
Transfer cooled biscotti to a cutting board and using a serrated edge knife, cut biscotti into 1½" thick slices at a slight diagonal. Place slices cut side down on the prepared baking sheet in a single layer leaving space between the biscotti. Return to oven and bake 10 minutes.
Remove from oven, carefully flip the biscotti to the opposite side and bake 5 minutes. Remove from oven and cool completely on a wire rack.
In a microwave safe small bowl, melt white chocolate with the half and half and maple flavoring in the microwave in 30 second intervals until melted and smooth.
Add the powdered sugar 1 tablespoon at a time and stir until thick enough to coat a spoon without running off. Use more or less sugar if needed.
Allow the maple glaze to dry completely before storing.