In a small casserole dish, lightly brown lard and onion.
Fold in butter and flour.
Pour broth into mixture.
Simmer a few minutes.
Add cooked tongue slices.
Season to taste with salt and pepper.
Continue cooking 10 minutes.
Meanwhile, whip mashed potatoes until fluffy.
Pipe a crown of mashed potatoes onto a serving dish.
Pile braised tongue slices into the middle of potato crown.