Place a 12” cast iron pan in the oven and preheat to 210C/410F (fan). Add the butter, let it melt, and heat for 5 minutes until light brown bits start to appear in the butter.
2 tbsp butter
Whilst the butter is heating, whisk together the remaining pancake ingredients.
150 g (1 cup + 3 tbsp) plain (all-purpose) flour, 3 large eggs, 240 ml (1 cup) milk - full or half fat, 2 tbsp sugar, 1 tsp vanilla extract, 1 pinch salt
Open the oven and working quickly (so the pan doesn’t cool too much) use a brush to brush the melted butter all over the inside (including the sides) of the pan. Quickly and carefully pour in the pancake mixture and close the oven.
Cook for 15-18 minutes until browned and risen.
Whilst the pancake is in the oven, make the blueberry sauce. Place the blueberries, water, and granulated sugar in a pan and heat for about 5 minutes until the blueberries release their colour and the sugar dissolves. Turn off the heat and put to one side to cool slightly.
Take the pancake out of the oven (the centre may be very puffed up, but it will go back down after a minute or two) and spoon in the blueberry sauce. Add a couple of scoops of ice cream and sprinkle with icing sugar.