Chocolate birthday cake advice please help!

[Lambzig]

I have a chocolate cake recipe that I normally bake in 2 8 inch round tins.

DS has requested this cake for his birthday, but I need to make it bigger.

I need to make a birthday cake in two 9 inch square tins. How do I change the ingredients/bake time.

Sorry if this is a dumb question, but I am a huge novice and can bake two cakes (the other is a Victoria sandwich).

If anyone has a foolproof chocolate cake recipe for nine inch square tins as an alternative I would be very grateful.

Any advice appreciated, including how much in advance I can make it (it will be decorated with fondant icing).

You need 1.5 times the original cake recipe (so 100g of flour becomes 150g etc).

It's DD2 party on Saturday and DP is baking the cake on Thursday pm and decorating it (with fondant) on Friday. The fondant will help keep the cake fresh.

HTG

With the bake times you can either cook it for the normal 8in round time and if not cooked add another 10mins on, then repeat. Do you know how to test if a cake is cooked? (Stab the cake in the centre with a Wooden skewer/knife - if it comes out clean it's cooked).

The other way is to wait till it smells like a cooked cake - with fan forced ovens the smell radiates through the kitchen :)

If the cake is looking a bit crispy on the edges wrap brown paper around the outside of the tin.

Use strips of damp tea towel pinned to the outside of the tin to prevent the edge burning. Turn the heat down a bit and bake for longer.

All fantastic advice thank you. Might have a practice this weekend. DS's birthday is on Sunday afternoon and we have people staying sat morning until Sunday lunch so I was hoping to make it Saturday morning.

Fill your usual tin with water then pour it into a jug to see the capacity. Let's say it's 500ml. Fill the bigger tin with water and do the same. Compare volume - if the bigger tin holds 1000ml obviously you'd double the recipe, If it's 1500, triple it, etc.

Gosh that sounds so obvious now you say it like that!

Eh, don't worry, I'm not a genius or anything, I just remembered reading it in a cake book