In a large mixing bowl, add flour, sugar and mixed spice, mix well. Add sultanas, chopped raisins and mixed peel, mix until well combined and set aside.
Pour hot water into a heat-proof jug or bowl and add chopped butter, mix until butter has completely melted, you can leave this aside to melt.
Pour the chilled water into a measuring jug or bowl and stir through brandy. Add baking soda and mix until dissolved.
Pour both the melted butter liquid mixture and brandy mixture into the dry ingredients. Gently mix with a wooden spoon until well combined.
Cover bowl with plastic wrap and sit on kitchen bench, in room temperature, overnight. This will allow the batter to thicken overnight.
The following day, fill a large pot half way up with hot water. Put over high heat and bring to a boil. NOTE: ensure you use a large enough pot that your pudding basin will fit comfortably into, with enough room around the sides for steam. Once the basin is inside the pot, the lid to the pot must fit on and leave no gap, meaning the pudding basin must not be taller than your pot. I use a 2-litre,
7-inch high, pudding basin,
Liberally grease a large pudding basin/tin with butter. Place a piece of baking paper on the flat base of the basin, to help remove the pudding later.
Uncover pudding batter and gently pour into greased pudding basin. Cut a round piece of baking paper enough to cover the top of the pudding and place it on the pudding. Then cover the top of the basin with a layer of foil, to enclose, this will keep the steam inside the basin to allow cooking.
Once water has come to a boil, reduce heat to medium and carefully place the basin into the water, sitting in the middle of the pot. Top up pot with more hot water so it reaches ½-3/4 of the way up the pudding basin.
Leave heat on medium, pot covered with lid and pudding inside, cook/steam pudding for 4-6 hours. You’re looking for a gentle boil, not a rapid boil and not a slow simmer. You’ll be keeping an eye on the pot throughout cooking and topping up the water when needed, as it does evaporate.