Heat the butter and olive oil in a large saucepan. Add the next 5 ingredients and sauté for 1 minute. Add the chicken stock, half & half and milk and bring to a boil. Remove from heat and slowly sprinkle the cornmeal into the hot milk while stirring constantly with a whisk. Cook over low heat, stirring constantly for a few minutes, until thickened and bubbly. Turn off the heat, stir in the Parmesan, pour into a 9 x 13-inch pan, smooth the top and refrigerate until firm and cold. Cut the chilled polenta into squares, lift out of the pan and then cut squares into triangles. Dust each lightly with flour. Heat 1 tablespoon olive oil and 1 tablespoon butter in a large sauté pan and cook the triangles in batches over medium heat until browned on the outside and heated inside. Serve with tomato sauce.