Add the first 4 ingredients into a saucepan and reduce on medium heat, until only about a cup of liquid remains. The sauce will thicken slightly as it reduces. Be careful not to reduce too far, as the sauce will burn. Season with salt and pepper to taste. Keep warm.
Salt and pepper the foie gras slices generously on both sides. Heat a dry skillet over high heat until very, hot (this is key!). Seared the slices for 1 to 2 minutes per side. The foie gras will brown and should be heated through, but removed before the slices begin to shrink significantly and lose too much of their fat.
Place the toasted bread on the plate, top with the seared foie gras, and spoon over the sauce. Serve immediately.
