For the blender:
Preheat the oven to 400º F.
Quarter or half all tomatoes, depending on whether they are large or medium in size, and place them in a single layer on a large baking sheet. Scatter all eight garlic cloves throughout the tomatoes, and drizzle with 1-2 Tbsps of olive oil. Finish with a couple pinches of salt and place all 5 sprigs of thyme over the tomatoes.
Roast the tomatoes for about 30 minutes or until they’ve begun to look wilted and softened.
Meanwhile, place a pan over medium heat and drizzle some olive oil for sautéing. Once hot, add the onions, stirring occasionally. Once the onions have become slightly translucent, add the red pepper flakes. Continue to stir occasionally, until the onions are quite soft. About 3 more minutes. Once finished, remove the pan from the heat and set aside.
Once the tomatoes are done, remove them from the oven and set them aside to cool slightly. Once they’ve come down in temperature, discard the thyme sprigs and transfer the rest of the contents of the pan (including the juices), and the onion mixture, to a high-powered blender.
Blend the mixture on high speed until very smooth.
NOTE: Depending on the types of tomatoes you used and the amount of liquid they released, the tomato mixture can vary in thickness. This will come into play in the following steps.
For the pot:
Place a large pot over medium heat. Once hot, add 1 tbsp of oil and 1 tbsp of butter. When the butter begins to foam, add 2 tbsp of flour and whisk constantly for about 2 minutes. The mixture should darken in colour. Then, slowly add 2 cups of the stock, continuing to whisk constantly and allow the mixture to thicken.
Pour the contents of the blender into the pot, combining it with the thickened stock. Depending on the consistency of the soup at this point, consider adding the remaining 2 cups of stock. Keep in mind that you will have a higher yield if you do, but the soup should remain a thickened consistency.
Stir in 1 tbsp of balsamic reduction, and add the parmesan rind (if using). Bring mixture to a light boil, and lower to a simmer for about 20 minutes, stirring occasionally, and salting to taste.
Toppings:
Meanwhile, place a pan over medium heat and add the chopped prosciutto. Since the prosciutto is quite oily to begin with, there’s no need to add oil to the pan. Stir frequently until the prosciutto is crispy and brown (about 3-5 minutes), then transfer the meat to a plate and return the pan to the heat.
Melt 2 tbsps of butter in the pan. Once it begins to foam, add the cubed bread, mixing until coated in butter. Stir the bread occasionally until the bread is crispy and golden (about 5 minutes).
Combine:
Once the soup has had time to simmer, carefully discard the parmesan rind. Salt + pepper to taste one last time, if necessary, before transferring the soup into bowls. Top with the croutons and fried prosciutto, and enjoy!