Make the soup:
1. Preheat the oven to 180C/160C fan. Slice the tomatoes in half and place them cut side up on a large rimmed baking sheet. Add the onion and garlic then drizzle generously with olive oil. Roast for 1 hour.
2. Bring the stock to a simmer in a large saucepan. Add the roasted vegetables and stalks of basil leaves. Simmer for 15 minutes then remove the basil and use a stick blender to blitz to a thick soup, adding a bit more water if needed. Add the salt and sugar, taste, then add the creme fraiche and mix through. Serve immediately, with an extra drizzle of olive oil if you like.
Make the grilled cheese roll ups:
1. Prepare the roll ups while the tomatoes are roasting. Cut the crusts off each slice of bread then butter lightly. Place 1 Castello Cheddar Slice on each piece of bread, leaving a gap at the end of the bread farthest from you. Use this gap to stick down the end of the bread to itself as you roll it up into a tight cigar shape. Repeat with the rest and put to one side until you’re almost ready to serve.
2. Heat 1 tablespoon of butter and 1 tablespoon of oil in a skillet. Cook 2 or 3 roll ups at a time, turning often to get an even golden brown colour. Serve hot, with tomato soup to dunk in.