Flour (or even cornflour) in curry? No way! Just make sure there's enough onion in the curry paste in the first place.

I experimented with a Thai red curry again the other day; the paste for this makes use of peanuts. The first time I made it I used peanut butter, which worked very well. The other day I used plain unsalted peanuts; also worked well, but I think I overdid it a bit: the sauce ended up very rich.