Add milk to small saucepan, over medium low heat bring to just under a boil.Ìý
Meanwhile, in a large saucepan melt butter over medium low heat, once butter is melted add flour and whisk vigorously for 1 minute, carefully add the milk, whisking continuously until it becomes thick, about 2 minutes.
Remove from heat, let cool slightly. Whisk in egg yolks, one at a time, add salt, cinnamon, grated onion.
In a standing mixer fitted with a whisk attachment, add egg whites. Begin whisking on low for a few minutes. Once the egg whites start to foam, gradually increase speed. Slowly add sugar and whip until sift peaks form. Careful not to over whip.
Using a large spatula, add one scoop of egg whites to the carrot mixture, stirring well to fully incorporate and lighten the mixture. Add half of the remaining egg whites, gently folding to in- corporate, fold in remaining egg whites.