First puree the garlic in a food processor.
Add the cod's roe little by little until combined.
With the processor still running, add olive oil in a thin stream, until you have a smooth paste.
Next add some lemon juice to taste.
Switch off the machine and you may find some olive oil has floated to the top. Switch on the machine again and add some breadcrumbs, a few at a time, until the excess oil has been absorbed.
Turn the Taramosalata out into a bowl and chill until required.