@Rachael
My normal recipe for a 6x3-inch recipe is:
150 Grams of Butter or Margarine
150 Grams Sugar (Caster or Granulated)
150 Grams Self-raising Flour
3 medium eggs.
Bake at 150°C - Fan assisted for about 50 mins.
However, I found that to get the height I wanted in my 6x3-inch tin, I was better using my 7x3-inch recipe of 200 grams of butter, sugar, flour, and 4 eggs. I use the creaming method for the recipe.
The thing with the Victoria Recipe is it's very versatile and can be doubled up, so for the
8x3 inch version, there are a few things you can do. The simplest way is just to double up and use 300 grams of butter or margarine, sugar, self-raising flour, and six medium eggs. You can then pour the mixture into your tin and see how 'full' you want it. If there is any mixture left, you can make cupcakes with it.
The other converted methods are as follows:
I will show you the estimated converted 6x3 inch tin recipe to 8x3 inch tin using the tin conversion method.
Then, apportion the ingredients on a 50-gram, 1-egg basis.
6x3-inch - 150 Gram Recipe converted to 8x3inch Tin: (Surface Area - 50.24/28.26 = 1.77 = 1.8)
270 Grams Butter or Margarine
270 Grams of Sugar (Caster or Granulated)
270 Grams Self Raising Flour
5.4 Eggs - Or 5 and Half Eggs (Just beat one in a bowl and use half the egg)
50 Gram Ingredients - 1 Egg Basis
By this, I mean for every 50 grams of ingredients I use in the sponge recipe, I use one egg, so as a rough guide, you could use the following:-
275 Grams Butter or Margarine
275 Grams of Sugar (Caster or Granulated)
275 Grams Self Raising Flour
5.5 Eggs - (Just beat one in a bowl and use half the egg)
Looking at the conversions, they are comparable, so it's up to you which route you wish to take. The easiest one to use would be the 275 mix but like I say it all depends on the height you want on your cake so if you want more height do the 300 gram mix and then gauge the amount in your tin.
You will also have to adjust the baking time because the cake is bigger, so I would bake it for 1 hour and then test it with a skewer. I don't think it will be done then, and it may need more time, possibly another 5 - 15 minutes, depending on your oven, but you can check on it in increments of 5 minutes depending on how much goo you had on your skewer. If it's clean, though, then take it out. I would still keep it to 150°C for fan-assisted.
I hope this helps and I haven't overloaded you with information. The simplest conversions and more rounded conversions generally work out the best. But I'm unsure if you want height on your cake or if you just want a regular conversion of a recipe.
This is what I mean by height on the cake; we worked this out for one of the members because she wanted more height on her cakes.
They came out perfect xx
If you need anything else, please let me know; if not, good luck and happy baking!