Tomato Sweet Potato Bisque with Pesto Grilled Cheese Croutons
1 medium sweet potato
1 tablespoon olive oil  
2 medium carrots, roughly chopped  
1 rib celery, roughly chopped  
1 sweet onion, roughly chopped  
1/2 teaspoon kosher salt, plus more as needed
4 cloves garlic, peeled and chopped  
2 sprigs fresh thyme  
1 bay leaf  
One 14.5-ounce can fire-roasted diced tomatoes  
1/4 teaspoon cayenne  pepper
4 cups unsalted vegetable broth,  or more as needed
1/4 cup heavy cream  
Freshly ground black pepper  
Micro basil, for garnish  
Pesto Grilled Cheese Croutons, recipe follows
2 cups packed fresh basil
2 cloves garlic, roughly chopped  
1/4 cup pine nuts, toasted  
1/4 cup freshly grated Parmigiano-Reggiano
1 teaspoon lemon zest  
Pinch kosher salt, plus more as needed  
1/4 cup extra-virgin olive oil  
Eight 1/2-inch slices bread, cut from a loaf of pain de mie
4 slices sharp or extra-sharp aged Cheddar, thinly sliced  
3 tablespoons unsalted butter, softened  
3 tablespoons mayonnaise  
Instructions:
Preheat the oven to 425 degrees F.
Place the sweet potato on a baking sheet and bake until soft, 35 to 40 minutes. Allow to cool, then peel it.
Meanwhile, heat a large deep skillet over medium-high heat. Add the olive oil and heat until just hot. Add the carrots, celery, onion and salt. Cook, stirring occasionally, until the onions just turn translucent, about 5 minutes. Add the garlic, thyme and bay leaf and cook, stirring occasionally, until the vegetables are nice and brown, 5 to 7 minutes.
Stir in the tomatoes with their juices and cayenne, then stir in the broth. Bring to a boil, then reduce the heat to maintain a steady simmer until the carrots are tender, about 15 minutes. Remove and discard the thyme sprigs and bay leaf. Add the roasted sweet potato.
Using a blender, puree the soup until silky smooth. Return the soup to the skillet and heat on low. Stir in the cream. For a thinner soup, stir in more broth. Season to taste and serve hot with the micro basil and Croutons.
To the bowl of a food processor, add the basil, garlic, pine nuts, Parmesan, lemon zest and salt. Pulse until the mixture forms a chunky paste, scraping down the sides and bottom of the bowl occasionally. With the machine running, add the olive oil in a steady stream. Keep processing until the desired consistency is reached, pulsing less for a more coarse pesto and more for a smooth one. Season to taste.
To make the sandwiches: Spread some pesto on 1 side of 2 slices of bread. Arrange a slice of Cheddar over the pesto on 1 slice of bread. Sandwich with the other slice of the bread, pesto-side down. Repeat with remaining pesto, bread and Cheddar.
Mix the butter and mayo together in a small bowl. Spread a generous layer on both sides of each sandwich.
Place the sandwich in a nonstick skillet and turn the heat to medium-low. Cook, turning occasionally, until the bread is nice and toasty and golden brown, the cheese is melty and the sandwich is heated through. Repeat with the remaining sandwiches. Cut into croutons.
