The beauty of these delicious sandwiches is that they can be prepared for future use and then removed from the freezer and baked in the oven as needed.
In a large bowl, combine softened butter, mayonnaise, Dijon mustard, chives, and thyme until well mixed.
Using a sharp bread knife, cut each bun in half horizontally.
Spread the butter mixture on the cut side of the bottom half of each bun. Layer with ham slices and cheese. Cover with the top bun half (do not spread mixture on this side). Wrap each sandwich tightly in foil. Refrigerate for 30 minutes to 2 days (optional if baking immediately).
Preheat oven to 180°C (356°F).
Place foil-wrapped sandwiches on a wire rack in the preheated oven. Bake for 20–25 minutes.
To bake later, freeze wrapped sandwiches for up to 1 month. To bake from frozen, thaw at room temperature for 30 minutes, then bake at 180°C (356°F) for 20–25 minutes.