Just did this yesterday night, i.e. break/restore Mirror:

1. restore Full backup with NoRecovery

2. restore all sequential TrLog backups with NoRecovery

3. setup partners on Principal and Mirror to point to each other:

ALTER DATABSE DB_Name SET PARTNER = PRT_Name

4. At this moment Mirror session should start automatically

5. Change Safety Mode if not High Safety (defualt)