Preheat the oven to 200C/180C Fan/Gas 6. Line an 8 inch square baking tin.
In a medium saucepan, heat the butter, brown sugar, granulated sugar and chopped dates on a low/medium heat until all combined - stirring regularly.
Optional: Blend this together using either a stick blender/electric whisk to create a pulp (if you don't want any of the date texture - I leave mine a little chunky).
Pour this mixture into a large bowl/the bowl of a stand mixer. Add the vanilla and eggs and combine again.
Fold in the flour and baking powder. Pour this batter into the lined tin and bake 30 minutes.
Remove and let cool on a wire rack. Once cooled, make the sauce by combining the butter, sugar and cream in a small saucepan and heating together on a low heat until combined. Add in the chopped nuts, stir and pour over the blondies. Sprinkle over a little salt then let set 20 minutes or so before slicing and serving!