What is Bird's Custard Powder?

Given my enthusiasm for Nanaimo bars, here's a question I am often asked: What is Bird's custard powder?

I understand the question, because it is one I had, too, in the beginning of my Nanaimo-bar-making journey.

The general consensus in Canada and beyond is that this stuff is a vital ingredient in the bars...but why? 

Bird's Custard Powder

Traditionally, the middle section of Nanaimo bars is made with Bird’s Custard Powder. This is a popular custard powder invented in the UK that immigrated to British Columbia in the early 1900s when there was a large wave of new immigration from Europe. This would have been well timed with the advent of iceboxes as a common household item in Canada, which would explain for the bar’s UK influence.

Instant vanilla pudding powder will do in a pinch, but do try to find Bird’s Custard Powder for a truly authentic taste. It’s not extremely difficult to find: look for it in the international aisle of your local grocery store, or online.

These may be of interest with that knowledge in mind:

Have you ever tried a Nanaimo bar?