Slightly flatten the pepper quarters and place on a baking sheet. Wrap the garlic in foil and place on the sheet. Roast in a preheated oven, 220°C (425°F), Gas Mark 7, for 30–40 minutes until the pepper is slightly charred and the garlic is soft.
When cool enough to handle, remove the skin from the pepper and discard. Transfer the flesh to a bowl.
Squeeze the roasted garlic flesh from the cloves into the bowl.
Using a fork, roughly mash the pepper and garlic together. Stir in the yogurt and spring onions. Season to taste with pepper and serve with the vegetable batons.