1. Crisp Crackling Crusts

Question

2. Crispy Crackling Crusts

(Which one is correct? Are both OK? What is the meaning of 'crackling'")

Answer 1

Both are correct.

Crackling implies a crispy texture. Here's the definition from Dictionary.com.

"to make slight, sudden, sharp noises, rapidly repeated."

When you eat these crusts, you crunch on them, making a slight, sharp noise with your teeth.