I like poussins for griddling, because they cook quickly and this stops the meat from drying out. Even so, they are better marinated, because they are young birds and are not the most flavoursome.
To spatchcock them all you need to do is cut along the backbone with strong kitchen scissors or poultry shears.
The marinade I used was chipotle chilli powder, epazote, lemon juice, olive oil, salt and pepper. I griddled the poussins skin side down in a ridged cast iron pan and then turned them over and finished them off in the same pan in the oven for about 15-20 minutes.
I made two salads to go with them, a kind of chunky version of guacamole and a chicory and orange salad with an orange juice, cider vinegar and olive oil dressing.
I also cooked some plain white rice to provide some bulk to the dish.