In a heavy medium saucepan, bring the water to a boil over high heat. Stir the polenta and salt into the water, lower the heat to medium-low and simmer, covered, stirring from time to time. Cook until the polenta is cooked through and thickens, about 20 to 25 minutes.
Remove the pan from the heat and stir in the cheese and jalapenos until smooth. Pour the polenta into a lightly oiled, shallow baking dish. Cover tightly with plastic wrap and refrigerate until firm, at least 6 hours and up to 2 days in advance.
Run a knife around the edge of the baking dish and unmold the polenta onto a cutting board. Cut into 3-inch by 3-inch squares and keep cool, wrapped, until ready to grill.
Yield: 4 to 6 servings