Heat 2 tbsp olive oil in a non stick pan over medium high heat. Add onion and cumin. Cook, stirring often, for 5 minutes or until the onion is soft.
Increase heat to high. Add mushrooms and cook, stirring occasionally for 5 minutes or until all moisture evaporates.
Set aside to cool.
Meanwhile, place the chickpeas, 2 tbsp yoghurt, tahini, 1 tbsp lemon juice and 1/4 cup oil in a food procesor. Process until smooth. Transfer to a medium bowl. Process the mushroom mixture until finely chopped.
Stir the mushroom mixture, remaining yoghurt and 1/3 cup chives into the chickpea mixture. Season with salt and pepper. Cover and refrigerate for 1 hour or overnight, if time permits.
Sprinkle the remaining chives over the hummus. Drizzle with the remaining 1 tbsp olive oil. Serve with crackers or crispbread.