In a medium-sized bowl, mix together the Gruyère cheese and fresh breadcrumbs, and set aside.
Place a small saucepan over medium heat and add the butter. Once melted, add the flour, whisking to create a roux.
Slowly incorporate the milk, whisking all the while, to create a thick and creamy béchamel sauce. Stir in the fresh thyme, lemon zest and juice, and salt, then remove the sauce from the heat.
Place the artichoke hearts into an ovenproof dish, then pour over the lemony béchamel sauce and top with the Gruyère mixture and black pepper.
Bake for 20-25 minutes until the artichoke mixture is bubbling and the top is golden and crisp. Serve hot.