Preheat oven to 180C/160C fan/350F.
Pour the milk in a saucepan and heat until it starts to bubble, take off the heat before it starts to boil.
Add the dates to a heat-proof bowl and pour over the hot milk. Leave to soak for 30 minutes.
Add the date & milk mixture to a blender/food processor and blend into a smooth paste.
Pour into a bowl along with the tahini and oil. Mix to combine.
Add the oat flour, baking powder, cinnamon and salt. Mix until you have a smooth batter.
Transfer into a 8x8 square cake tin lined with parchment paper and sprinkle the chopped walnuts on top.
Bake for 40-45 minutes or until a clean skewer inserted in the middle comes out clean.
Allow to cool completely before slicing. Mix the drizzle ingredients in a small bowl and drizzle over the cake before serving.