In a large, deep pot, bring chicken broth to a gentle boil over moderately high heat. Stir in the salt. Reduce the heat slightly and slowly add cornmeal, whisking constantly. Reduce the heat to low and cook, whisking often, for 15 to 20 minutes, or until thickened. Remove from the heat and transfer the cornmeal mixture into a lightly oiled pie plate. Spread the mixture evenly over the bottom of the pie plate.
Preheat the oven to 350 degrees.
In a large skillet, melt the butter over medium heat, add the mushrooms, and sauté until the mushrooms are light brown. Season with the sherry, salt, and pepper. Top the cornmeal mixture with the mushroom mixture and Robiola cheese cubes. Bake for 45 minutes.
Set oven temperature to broil and lightly brown the cheese. Cut into 8 wedges and serve immediately.