Broughton, 30, is traditionally a specialist over marathon distances, but shocked the world in the K1 1000m final.
The Brit broke the line in 4:03.927seconds to take silver behind Hungary’s Dora Bodonyi who defended her crown while South Africa’s Bridgitte Hartley took bronze.
Broughton does have some history in this event - she took World Cup gold in Duisburg in Germany in May but could not quite believe her achievement afterwards in Montemor-o-Velho.
"I was aiming for the final, then I thought about top five, and in the last 100m I thought about a medal. To get silver is amazing," she said.
Elsewhere in the C2 500m Katie Reid and Chloe Bracewell were fourth in their heat to secure smooth passage into the semi-finals.
But Matthew Bowley went out of the K1 500m at the semi-final stage while Thomas Lusty and Daniel Johnson could not progress any further than that in the K2 1000m. Sportsbeat 2018