In a medium saucepan over low heat, melt the butter and whisk in the flour. Cook, whisking constantly for 2 to 3 minutes to be sure the flour doesn't brown. Whisk in mustard, Worcestershire sauce, salt, and pepper until smooth. Add beer and whisk to combine then whisk in cream til smooth. Gradually add cheese, stirring constantly, until cheese melts and sauce is smooth; this will take 4 to 5 minutes. Add hot sauce to taste.
