Welsh Rabbit

Directions

1. 1
   Preheat broiler.
2. 2
   Spread one side of bread slices with 2 tablespoons butter (total), then arrange slices, buttered sides up, on a baking sheet.
3. 3
   Broil 4 to 6 inches from heat until golden brown, 1 to 4 minutes.
4. 4
   Melt remaining tablespoon butter in a 1-quart heavy saucepan over low heat, then add flour and cook, whisking constantly, 1 minute.
5. 5
   Add beer and milk in a stream, whisking, then whisk in mustard, pepper, and cheese.
6. 6
   Bring to a simmer over moderately low heat, whisking, then simmer, whisking, until smooth, about 2 minutes.
7. 7
   Remove from heat and immediately whisk in yolk.
8. 8
   Serve cheese sauce on toast.