They were comparatively easy to make and worked equally well in the brownie tin and in cupcake cases (where I put the extra mixture that wouldn't fit in the brownie tin, and baked for only 10 minutes). We had plenty to give to our friends and for us to eat at home, without any need to double the mixture.
The 3-year-old and the 1-year-old loved them and would cheerfully have eaten the whole tin. The partner was less impressed and felt they were "too chocolate-ey". I have to say that I agreed with the kids, and would definitely make these again - although I'd be tempted to add walnuts instead of chocolate chunks at the end.