They hadn't risen much but weren't a disaster. I left them on the side to cool and when I came back they had sunk, and when tasted didn't quite taste cooked in the middle. I was meant to be taking them to a party the following day and well I couldn't.
So I made a new batch the following morning using self raising flour and this was the result when cooled:
Much more risen and much better looking cakes! The two muffins below are a comparison, the top one is the second batch using self-raising flour, the bottom is the first batch using plain flour.
So I think the answer is use self raising flour when using American recipes to bake. Is there some kind of raising agent in all-purpose flour, which is what the original recipe called for? Is that why mine made with plain flour failed?
Pear and Honey Muffins (adapted from Crepes of Wrath)
(Makes 12-16 muffins)
275g self-raising flour
¾ tsp baking soda
½ tsp salt
170g unsalted butter, cubed
3 eggs, room temperature
½ tsp vanilla extract
1 pear, peeled, cored and mashed
1 pear, peeled, cored and diced
Preheat the oven to 180C. Line the muffin tins with paper cases.
Combine the flour, baking soda, and salt. In a mixing bowl, beat the butter until smooth and creamy, about 3 mins, then add in the honey and beat until combined. Add in the eggs, one at a time, until combined , then add in your vanilla and mashed pear.
Gradually fold in the flour mixture, then fold in the diced pear. Divide the batter amongst your paper cases. Bake for 18-20 mins. Allow to cool before removing from the tins.