Wilko stout (what sugar to use??)

[Farley]

Plan is
1. Can of Wilko velvet stout
2. 500g brewing sugar
3. 500g dark brown sugar
4. 250g treacle
5. 200g maltodextrin (for head retention)
Kit yeast
Question is do I need any DME??
Was hoping to get away without!

 

[AMyd666]

I'd replace the brewing sugar with dry malt extract