Melt butter in a saucepan over low heat; add flour, whisking until smooth. Cook, whisking constantly, 2 to 3 minutes. Whisk in beer; cook, whisking constantly, 3 minutes.
Stir in cheese and next 5 ingredients. Cook 3 to 4 minutes or just until cheese melts. Spoon over English muffins.
Broil 5 1/2 inches from heat 30 seconds or until browned. Serve with tomato slices, if desired.
Note: For testing purposes only, we used Sierra Nevada Pale Ale.