To make the hummus: Put the chickpeas in a pot and cover with a few cm of water. Add the bicarbonate of soda and cook for 20 minutes until tender. Drain and rinse with cold water.Combine all ingredients in a blender and blend until smooth. Add ice cold water if you do not have a strong blender and need more liquid.To make the mushrooms: Place a large frying pan on high heat. Drizzle a little olive oil and sesame oil into the pan. Fry the mushrooms until almost golden brown and then add the garlic and season with salt and pepper. Cook for a further 2 minutes until the garlic is golden brown. Remove from the heat and sprinkle the mushrooms with mixed sesame seeds.Top the hummus with the mushrooms and serve with toasted pita or flatbread.