For the fluffy vanilla cake with hot vanilla sauce from the slow cooker, put some oil in the insert of the slow cooker and spread with a piece of kitchen roll.
Mix the flour, powdered sugar, vanilla milk powder, baking powder and salt well in a bowl, add the vanilla milk, oil and vanilla sugar and mix until smooth, then add the ground walnuts and mix well.
Pour the mixture into the insert of the slow cooker and spread well. Combine the ingredients for the glaze and pour over the batter, put the lid on and cook on HIGH for 2.5 hours.
At the end of the cooking time, turn off the slow cooker, take off the lid and let cool for about half an hour.
Spoon the cake onto plates, pour the hot custard that has formed underneath over the cake and serve the vanilla cake with hot custard immediately.