This is a nice easy buttercream that can be used for under icing if you are using royal icing, or as a stand alone icing too. This is enough to ice the size of cake the vanilla buttermilk cake recipe is for — but generally, you always want twice as much icing sugar as butter and it works.

Vanilla Buttercream Icing


  • 500 gramme soft unsalted butter
  • 1 kilogram icing sugar
  • 1 teaspoon vanilla bean paste
  • 4 tablespoons milk


  • Beat the butter until white & fluffy
  • Slowly beat in the icing sugar, half a cup at a time
  • Add the vanilla and milk and beat in — make sure it’s really fluffy*

* One way to test is if when you take a small amount and roll it between your fingers, it should smear and NOT be possible to form into a ball. If you can form it into a ball, beat for longer!

This was the largest ever batch of buttercream icing I ever made — 2kg of butter and 4kg of icing sugar. It was such a big pile it had to be transported in bin bags!

Bin bag filled with vanilla buttercream icing

This Nigella birthday cake recipe is my go-to when I need something that will stay moist, be pretty plain but still delicious and not crumble or fall apart when carved.

Four vanilla buttermilk cakes in the roasting tins they baked in

Vanilla Buttermilk Cake


  • 250 gramme soft unsalted butter
  • 400 gramme caster sugar
  • 6 large eggs
  • 400 ml buttermilk
  • 1 teaspoon vanilla bean paste
  • 500 gramme plain flour
  • 3 teaspoons baking powder
  • 1 teaspoon bicarbonate of soda
  • 0.5 teaspoon salt
  • One 38 x 25 x 8cm H (15″ x 10″ x 3″) large roasting pan*, greased & lined with baking parchment


  • Preheat a convection oven to 160 degrees C (180 C if using a non-convection oven)
  • Mix the vanilla bean paste into the buttermilk
  • Sift together all the dry ingredients
  • Cream the butter and sugar together (ideally using a mixer — will take forever by hand!)
  • Reduce the mixer speed and beat in the eggs, one at a time, mixing for at least a minute in between additions
  • Reduce the mixer speed and slowly add the dry ingredients and the buttermilk vanilla, alternating each
  • Bake in the oven for 50 mins — you may need to cover it with tinfoil after the first 30 mins to keep the top from burning
  • Remove from the oven, leave to cool and then ice with vanilla buttercream icing

* I like this roasting pan from Lakeland.