Heat oil in a large stockpot over medium-high to 350°F.
Cook beer in a small saucepan over medium-high until reduced to about 3 tablespoons, about 15 minutes. Transfer to a small bowl, and refrigerate, uncovered, until ready to use.
Cut boudin into 1 1/2-inch-thick slices, leaving the casing intact, and place in a large bowl. Add 1/3 cup of the flour, and gently toss to coat. Set aside.
Stir together cornmeal, sugar, baking powder, cayenne, 1/2 teaspoon of the salt, and remaining 2/3 cup flour in a large bowl.
Whisk together eggs and milk in a separate bowl. Add milk mixture to cornmeal mixture, and stir just until combined.
Stir together reduced beer, mustard, sorghum syrup, vinegar, and remaining 1/2 teaspoon salt in a small bowl. Set aside.
Place 1 boudin piece into cornmeal mixture, and gently spoon cornmeal mixture over boudin, coating completely. Carefully stab boudin piece through casing with a toothpick. (This will hold the sausage piece together.) Lift sausage piece, and allow excess coating to fall off fritter. Using a spoon, gently push fritter off toothpick into hot oil. Repeat with remaining boudin pieces and coating mixture. Fry fritters, turning occasionally with tongs, until browned on all sides, about 7 minutes. Drain on paper towels, and serve with sauce.