Preheat the oven to 220°C fan.
Mix the peppers and oil and spread out on a large parchment-lined baking tray. Roast for 15 minutes, and then add the garlic. Continue to roast for 15 minutes, until the skin of the peppers is soft and starting to blacken and the garlic is golden-brown.
Place the peppers in a food processor, along with the garlic, thyme leaves, paprika, chilli flakes, vinegar, walnuts and ½ teaspoon of salt. Blitz to form a rough paste and set aside.
To make the mash, put the oil into a small saucepan and place on a medium heat. Once hot, add the garlic clove and thyme sprigs and fry very gently for 2-3 minutes, until the garlic starts to caramelise. Discard the garlic, and set the sprigs of thyme aside, along with 2 teaspoons of the oil. Pour the remaining oil into a food processor with the butterbeans, 1 tablespoon of water and ½ teaspoon of salt. Blitz until completely smooth, adding a little more water if you need to. Spread out on a large platter or a few plates, creating a natural rim around the edge, and spoon the red pepper sauce into the centre. Top with the crispy thyme sprigs and their oil.
