Peel the onions and carrots and clean the celery, trimming the edges.
Roughly chop the vegetables and add them in the blender, pulsing a few times until you have finely chopped veggies. Be careful not to blend them into a paste.
Fill a muffin tray or ice cube tray with the mixed vegetables, pressing well. Freeze overnight.
Remove the blocks of Soffritto from the trays and place them in a freezer bag, ready to use!
They will last in the freezer for 8 to 10 months.When you need them, put the block in cold oil and let them soften at low heat for 10-15 minutes.