Stir together the milk, water, thyme, parsley, rosemary, 1/2 tsp salt, and 1/4 tsp black pepper in a medium-size saucpean over medium heat. Cook, stirring often, until liquid just begins to slightly boil.
Reduce the heat to low then slowly pour in the cornmeal, just a little bit at a time (to keep from clumping), until fully incorporated.
Continue to stir until the cornmeal thickens, about 5 minutes.
Take the pan off the heat and stir in the Gruyere and butter until melted.
Taste and season with additional salt & pepper if needed.