Cooking wasn't Mom's strength. She hated cooking with a passion that burned as hot as the gas burners on our turn-of-the-century range. Since she had three daughters, we became the cooks as soon as we were old enough to reach the stove. But we were not allowed to change the recipes -- HER recipes. She sat on a stool in the corner of the kitchen and micro-managed every step, no matter how many times each of us had prepared that dish before.
I was the oldest. I still remember every miserable step of making this dish.
One-half stick of margarine goes into a large fry pan to melt. Once melted, add one-half cup of flour and mix thoroughly. Don't allow the flour/margarine mixture to brown up and gain flavor like a real roux! That would spoil the color! We're going for pasty white here!
Now add two to three cups of milk and stir over heat until the whole thing becomes a gluey white gravy. No matter how you stir, it will be lumpy -- the flour was uncooked and so won't incorporate well with the milk. But stir it anyway. Maybe this time ...
While the glue thickens, open a can of tuna packed in oil. DON'T DRAIN THE OIL! It adds flavor! Dump the canned tuna, oil and all, into the gravy and stir like crazy. You are desperately trying to keep that oil from forming a greasy layer on top of the white glue. It won't work, of course. Between the margarine that separated from the flour-that-was-not-roux and the tuna oil, the instant you stop stirring, about a half-inch of shining yellow oil will float to the top of the gluey white gravy.
When the tuna is heated through, you are ready to plate. Lay two slices of soft, white bread -- NOT TOAST -- on each plate. Spoon the tuna gravy over each. NOW call the family to dinner, so that by the time they reach their plates, the white bread will have disintegrated into a soggy dough-like substance under the gluey white gravy, with its shiny oil slick on top.
Salt and pepper to taste and dig in. Enjoy the thrill of never knowing whether the next soft white lump on your fork will be a bit of tuna, a blob of bread dough or a lump of uncooked flour.