Step 1Heat the milk in a small saucepan with the garlic and marjoram sprigs and bring just to a boil. Turn off the heat and allow to steep for 10 minutes. Remove and discard the garlic and marjoram.
Step 2Melt the butter in a saucepan over medium heat and whisk in the flour. Cook over low heat, stirring, 2 to 3 minutes. Slowly whisk in the warm milk and stir until very smooth. Crumble in two-thirds of the cheese and whisk until incorporated. Stir in 1/2 teaspoon of salt. Set aside to cool to room temperature.
Step 3Stir in the egg yolks.
Step 4Heat the oven to 375 degrees. Liberally butter a 2-quart straight-sided shallow baking pan or gratin dish.
Step 5Beat the egg whites with a pinch of salt until they hold soft peaks. Do not beat until dry. Thoroughly fold a quarter of the whites into the cheese mixture. Sprinkle in the chopped marjoram and pepper, stir to combine and fold in the remaining whites. Pour into the dish. Dot with the remaining cheese.
Step 6Place in the center of the oven. Bake until the top is puffed and golden brown, about 30 to 40 minutes. Serve immediately.