Heat a 4-6 quart heavy pot over low heat and add the diced bacon. Once it has rendered a few tablespoons of fat, increase the heat to medium and cook until the bacon is crisp and golden brown. Pour off all but 1 T. of the bacon fat, leaving the bacon in the pot. Add butter, onion, carrots and sage and sauté, stirring occasionally for 6 to 8 minutes, or until onion is tender but not browned, Stir in dry mustard and Jalapeno and cook for 1 minute more. Add potatoes, beer and stock. Turn up the heat, cover, bring to a boil and cook vigorously for about 12 minutes, or until potatoes are tender on outside but firm inside. Smash a few potatoes on the side of the pot to thicken chowder. Remove chowder from heat and stir in the cream. Season with pepper, then under season with salt. (grated cheese will add salt) Let stir at Room temperature for up to an hour, allowing flavors to meld. Reheat chowder slowly over low heat until it is hot but has not quite reached a simmer. Gradually stir in the cheese and continue to stir constantly until all the cheese has melted. Taste chowder and season again. Ladle into cups or bowls and garnish with sliced scallions