Hi Phil, Could it be because the Chicken is solid, whereas a spring roll is hollow with smaller bits inside it?
I would also guess, not basing this on fact, just supposition, that the fact that the spring roll is hollow, it's creating a convection type heating inside it, therefore, it heats up faster than a solid piece of chicken which heats up from the outside in. Make sense? No, I would think not, because that explanation even confused me. Smile. Victor Gouveia