In a large bowl, whisk together the flour, sugar, cornstarch, baking powder, salt and baking soda. In a separate medium bowl, whisk together the buttermilk, cream and eggs.
Using a wooden spoon, stir the wet ingredients into the dry ingredients until just a few streaks of flour remain and the batter is almost mixed together. Add the melted butter and stir until just combined. Let the batter rest for 15 to 30 minutes.
Heat a waffle iron according to manufacturer's instructions. Spray the waffle iron with nonstick spray. Pour 1 cup of batter into the iron and allow to cook 3 to 6 minutes for each waffle.