Preheat the oven to 375°F.
In a medium saucepan over medium heat, melt the butter. Remove from the heat and brush a small amount of the melted butter inside a 1-quart soufflé dish. Sprinkle grated Parmesan over the walls of the dish, shaking and rotating the dish to cover the surface evenly. Tap out the excess. Place the
dish in the refrigerator while making the batter.
In a small saucepan over medium low heat, warm the half-and-half and thyme until the mixture begins to steam. Keep warm over very low heat. In another saucepan over medium heat, warm the remaining melted butter.
Whisk in the flour and cook 2 minutes, whisking constantly. Do not let the
Discard the thyme sprig. Whisking constantly, add the warm half-and-half in a slow, steady stream to the saucepan with the flour mixture. Cook until the mixture thickens and comes to a simmer. Remove the pan from the heat, add the goat cheese, salt, mustard, and nutmeg, and stir until smooth.
In a medium bowl, beat the egg yolks. To temper the yolks, add half the warm half-and-half mixture to the bowl, 1 to 2 tablespoons at a time, whisking between each addition. Whisk in the remaining half-and-half mixture. Set aside to cool to room temperature.
In the bowl of a stand mixer with a whisk attachment and set on low speed, beat the egg whites until frothy. Add the cream of tartar and a pinch of salt, then beat on high speed until the mixture forms firm, glossy peaks. Fold the beaten whites into the egg yolk mixture in thirds, taking care to avoid
deflating the whites.
Pour the batter into the prepared soufflé dish. Bake until puffed, browned, and set, 22 to 25 minutes. Serve immediately, drizzled with honey, if using.