In a large pot or Dutch oven, heat the olive oil over medium heat. Add the onions and cook over medium-low heat for 15 minutes, stirring occasionally, until golden brown. Add the garlic and cook for 1 more minute. Stir in the chicken broth, tomatoes, saffron, 1 tablespoon kosher salt, and 1 teaspoon pepper. (At this point, I blend the soup to remove chunks for the kids). Bring the soup to a boil, then lower the heat and simmer for 15 minutes.
Meanwhile, fill a medium pot with water, add 2 teaspoons salt, and bring to a boil. Add the orzo and cook for 7 minutes. (It will finish cooking in the soup.) Drain the orzo and add it to the soup. Stir in the cream, return the soup to a simmer, and cook for 10 more minutes.
While the soup is simmering, heat a panini grill, electric skillet, or frying pan to medium. Place the four slices of bread on a cutting board and brush lightly with the melted butter, being sure to butter up into the corners. Turn the slices over and pile the grated cheese on two of the slices. Place the remaining two slices of bread on top of the cheese, buttered sides up.
Grill the sandwiches for about 3-5 minutes on each side, until nicely browned. Place on a cutting board, allow to rest for 1 minute, and cut into 1-inch cubes.
Serve the soup hot with Grilled Cheese Croutons scattered on top.
I make triple the Grilled Cheese Croutons for our family of six.
Source: Barefoot Contessa Foolproof by Ina Garten