In a medium saucepan over low heat, melt the butter and whisk in the flour. Cook, whisking constantly for 2 to 3 minutes, being careful not to brown the flour. Whisk in mustard, Worcestershire sauce, salt, and pepper until smooth. Add beer and whisk to combine. Pour in cream and whisk until well combined and smooth. Gradually add cheese, stirring constantly, until cheese melts and sauce is smooth; this will take 4 to 5 minutes. Add hot sauce. Pour over toast and serve immediately.
Recipe courtesy of Alton Brown, 2003