Creating the Feta Grilled Cheese Sandwich with Spinach is an enjoyable process. Follow these simple steps for a delightful meal:

1. Prepare the Spinach: In a skillet over medium heat, add olive oil and wilt the spinach for about 2-3 minutes. Season with salt, pepper, and garlic if using.
2. Spread Butter: On one side of each slice of bread, spread a generous layer of butter. This will help create a crispy, golden crust.
3. Assemble the Sandwich: On the unbuttered side of two slices, layer the wilted spinach followed by the crumbled feta cheese. Top each sandwich with another slice of bread, buttered side up.
4. Grill the Sandwich: In the skillet, reduce heat to medium-low and place the assembled sandwiches. Cook for about 3-4 minutes or until golden brown.
5. Flip and Cook Again: Carefully flip the sandwiches and grill the other side for an additional 3-4 minutes until the bread is golden and crispy, and the feta has begun to melt.
6. Slice and Serve: Once cooked, remove from the heat, slice the sandwiches in half, and serve hot.