The phrase "to crack the ice" means to break the tension or awkwardness in a situation by making the first move or starting a conversation in order to make people feel more comfortable. Full definition
Just remember, hearing the sharp pop of cracking ice is a good thing — it's when the cracking stops that it's time to get out and run. (automobilemag.com)
Add cracked ice and stir for 25 - 30 seconds. (tastingtable.com)
Transfer ice to a mixing glass and repeat until you've got enough cracked ice to fill glass. (bonappetit.com)