Lightly dry out the bread so it soaks evenly: set slices on a rack for 10 minutes or toast in a 275°F (135°C) oven for 5 minutes. Let cool while you make the filling.
Make the filling: In a medium bowl, beat the softened cream cheese with pumpkin puree, brown sugar, 1/2 teaspoon vanilla, 1/2 teaspoon pumpkin pie spice, orange zest, and a pinch of salt until completely smooth and fluffy.
Assemble the sandwiches: Spread the filling generously over two slices of bread (edge to edge). Cap with the remaining slices and press along the edges to help seal. Refrigerate 5–10 minutes to firm the filling.
Whisk the custard: In a shallow dish, whisk eggs, milk, maple syrup, 1 teaspoon vanilla, 1/4 teaspoon pumpkin pie spice, and a pinch of salt until no streaks of egg remain.
Preheat a large nonstick skillet over medium heat. Melt 1 tablespoon butter in the pan.
Dip each stuffed sandwich in the custard for 15–20 seconds per side, letting excess drip off. Lay in the hot skillet and cook until deep golden, 3–4 minutes. Flip, add the remaining 1/2 tablespoon butter, cover the pan for 1 minute to help the center heat through, then uncover and cook 2–3 minutes more until the exterior is crisp and the filling is warm.
Rest 1 minute before slicing. Serve warm with a dusting of spice or a drizzle of maple syrup, if desired.