Step 1

In a large sauce pan over medium heat, melt the butter.

Step 2

Add the flour to the melted butter. Stir to combine. Allow the mixture to warm over the heat for 1-2 minutes.

Step 3

Start pouring in the milk, a little at a time, stirring after each addition to prevent lumps.

Step 4

When all of the milk is added, continue stirring until the sauce thickens. You're looking for a thick gravy texture.

Step 5

Stir in beef and salt and pepper to taste. Continue cooking for 1-2 minutes, until roast beef is heated through.

Step 6

Serve warm over toast.