Smoked Salmon Croque Madames

INGREDIENTS

• 5 tablespoons unsalted butter, softened
• 1 tablespoon all-purpose flour
• 2/3 cup whole milk
• Coarse salt and freshly ground pepper
• 8 slices white Pullman bread, or thinly sliced sandwich bread
• 2 tablespoons Dijon mustard
• 5 ounces smoked salmon
• 1/4 cup small dill sprigs, plus more for garnish
• 2 cups grated Comte cheese
• 4 large eggs