Heat oil in a large skillet over medium heat. Add the shallot and cook, stirring constantly, for about 2 minutes. When fragrant and just about translucent, add the garlic, dill and spinach, about 2 handfuls at a time. Sauté, stirring constantly, until all spinach has cooked down and is vibrant green, about 2 to 3 minutes. Transfer to a medium bowl.
To the spinach mixture, stir in the Feta and cream cheese until incorporated.
Butter one side of each slice of bread. Lay out the slices butter-side down and then add the sliced cheese to two pieces of bread. Divide the spinach mixture between the two cheese-topped pieces of bread. Lay the remaining bread slices on top, butter-side up.
Preheat a large skillet over medium-low heat. Add the sandwiches and allow to toast about 3 minutes a side, flipping once, until bread is golden and toasty, and cheese is melty (keep an eye the bread doesn’t over-toast; adjust heat as necessary). Tip: If you weigh down the sandwiches with a lid that’s slightly smaller than the skillet, it helps ensure an even toasting and helps keep the sandwich together.)
Allow sandwich to rest about 3 minutes before slicing. Serve with a glass of chilled Rudy Sauvignon Blanc.