Adding nuts to a cake recipe

[Lones80]

We are having a bake off at work and I have to make a Toffee & Walnut cake (I've checked and it's definitely not meant to be coffee and walnut). I've found a lovely looking recipe for a toffee cake and I'm wondering how best to add the nuts. Can I blitz them and replace some of the flour with the ground nuts? If I do, should I add extra rising agent?

Thanks!

If you blitz them, you'll hardly know that they're there.

I'd chop them finely - too large pieces and they'll sink to the bottom, too small and they won't be noticeable.

I'd chop them so that they're a little larger than the nibbed nuts you can buy in packets.