Par-boiled frozen Japanese sweet potato, roasted

Wash two Japanese sweet potatoes and chop into chunks.

Boil in a pot of water with a big handful of salt to part-cook, 10 minutes; this turns some starch to sugar and prevents enzymatic browning in the freezer.

Strain, spread on a baking sheet and freeze; once frozen, bag in portions.

To serve, toss the frozen sweet potato with olive oil, garlic powder and oregano and roast, about 10 minutes.