Heat a non-stick skillet over medium-low. Add a bit of oil and cook the leeks and garlic until soft, 5 minutes. Add the spinach and cook until just wilted, 2 minutes or so. Remove the spinach mix and set aside.
Assemble the grilled cheese: butter the outsides of the bread and lay the slices on a cutting board, buttered sides facing down. On the un-buttered sides, spread the pesto evenly. On one slice, layer half of the shredded cheese, then the avocado slices and spinach mixture. Top with the remaining shredded cheese and the other slice of bread, butter side facing out.
Use the same non-stick skillet as before and heat over medium. Carefully move the sandwich to the pan and fry until golden brown and crispy, flipping once.
Notes: Jessica’s sandwich is perfect as is, but I couldn’t resist using butter instead of olive oil and adding in some thickly sliced avocados. I’m pretty sure she would approve.
