Croque Madame Mini Quiches and Dijon Béchamel

Name: Croque Madame Mini Quiches and Dijon Béchamel
Ingredients: All-purpose flour, for dusting; 1 sheet frozen puff pastry, thawed; 1 tablespoon olive oil or unsalted butter; ½ small sweet onion, diced; 1 garlic clove, grated; 6 large eggs; ¾ cup heavy cream, divided; ¼ teaspoon freshly grated nutmeg; Salt and ground black pepper to taste; 4 ounces ham, diced; 1½ cups shredded Gruyère cheese; 1 tablespoon fresh thyme; 2 tablespoons chopped fresh chives; 1 tablespoon unsalted butter; 1 small garlic clove, grated; 1 tablespoon all-purpose flour; ¾ cup whole milk; 1½ teaspoons Dijon mustard; Salt and pepper to taste