Adjust rack to top position and preheat oven to 425 degrees. Wash and dry produce.

Cut potatoes into ½-inch-thick wedges. Toss on a baking sheet with a drizzle of oil, oregano, salt, and pepper. Roast on top rack until browned and tender, 20-25 minutes.

While potatoes roast, peel and mince or grate garlic. Quarter lemon. Thinly slice tomato into rounds and season with salt and pepper.

Pat chicken* dry with paper towels; season all over with salt and pepper. Heat a drizzle of oil in a large pan over medium-high heat. Add chicken; cook until browned and cooked through, 3-5 minutes per side. Turn off heat; transfer to a plate. Wipe out pan.

In a small bowl, combine mayonnaise, mustard, ¼ tsp sugar (½ tsp for 4 servings), juice from one lemon wedge (two wedges for 4), and a pinch of garlic. Season with salt and pepper to taste.

Heat a drizzle of oil in a large pan over medium-high heat. Add spinach and remaining garlic; season with salt and pepper. Cook, stirring, until spinach is wilted, 2-3 minutes.

Turn off heat. Transfer spinach to a second small bowl; stir in cream cheese until combined.

Wipe out pan.

Use pan used for chicken here.

Spread half the sourdough slices with creamy spinach; top with even layers of feta, mozzarella, and tomato.

Spread remaining sourdough slices with Dijonnaise (save some for serving).

Close sandwiches.

Top creamy spinach with chicken along with feta, mozzarella, and tomato.

Melt 1 TBSP butter in pan used for spinach over medium heat. Once hot, add sandwiches and push around in pan until melted butter has absorbed. (For 4 servings, work in batches or use a second pan, using 1 TBSP butter for each batch.) Cook until bread is golden brown and cheese is slightly melted, 4-6 minutes.

Add another 1 TBSP butter to pan, then flip sandwiches and push around again until melted butter has absorbed. Cook until bread is golden brown and cheese is fully melted, 4-6 minutes. TIP: If you have a heavy-bottomed pan, place on top of the sandwiches as they cook for a real panini experience!

Squeeze one lemon wedge over potatoes (two wedges for 4 servings).

Halve panini on a diagonal and divide between plates. Serve with potato wedges and remaining Dijonnaise on the side for dipping.