Add the cornmeal to a large bowl along with the flour, baking powder, salt, basil, sage and thyme and stir together.
Measure the buttermilk in a measuring cup, add the whole milk and egg and stir together with a fork. Add the baking soda and stir. Pour the milk mixture into the dry ingredients and stir with a fork until just combined. Do not overmix.
In a small microwave-safe bowl, melt 2 tablespoons butter and 2 tablespoons shortening in the microwave and slowly add to the batter, stirring constantly until combined.
In a 10-inch cast-iron skillet over high heat, melt the remaining tablespoon of butter and shortening. Pour the batter into the hot skillet, spread to even out the surface and cook over high heat for 1 minute. Then get it into the oven straightaway and bake until golden brown, 20 to 25 minutes. The edges should be crispy.