Never made mustard mash before, sounds pretty good. A variation I like is to mix some chopped scallions in with the mash just before you beat it, can also add a little grated cheddar for a really tasty treat.
Might it be prudent to suggest he waits until it is confirmed that the fire on Western Road has been extinguished, just in case things go totally Pete Tong and he needs the men with the squirty things?
Don't put them in the toaster unless you never want to use it to toast bread again, probably the best way (healthiest) to cook them is by baking, alternatively you could pop them under the grill.