Heat oil in a small frying pan over medium-high heat. Add onion and garlic, sauté until tender (5-10 minutes). Transfer to a large bowl and set aside to cool to room temperature.
Meanwhile, blanch spinach and chicory until just tender (5-10 seconds), then refresh. Drain, squeeze out excess water, coarsely chop and add to onion mixture with remaining ingredients. Season liberally to taste and refrigerate until required for rotolo di pasta ripieno recipe.