Preheat oven to 160 C / Gas 2/3. Grease a deep baking tray and line with baking parchment.
Separate eggs, place whites in a bowl and whisk until stiff peaks form and the whites do not move when the bowl is tipped. Set aside.
In a separate bowl, whisk the yolks with the sugar until light and creamy. Add the margarine and vanilla paste and beat for about 2 minutes. Add flour and mix all together until it's all well combined. Slowly add the warm milk, beating well until everything is mixed together.
Add the egg whites, a third at a time, gently folding all the mixture together, repeating until all egg whites have been added. Try not to lose any air. Pour the mixture into the prepared baking tray and sprinkle with cinnamon.
Bake in the preheated oven for about 1 hour or until firm and the top is golden. Remove from the oven and allow to cool fully, about 90 minutes.
Once cool, dust heavily with icing sugar, cut into bars then serve and enjoy!
Also lovely served with fruit, fruit coulis or jam. Let me know how you like it best :)