Grind the wild rice to as fine a powder as you can in a spice grinder, working in batches if needed, then combine with the remaining ingredients and chill/rest for at least a few hours before cooking, and preferably overnight as it can take time for some of the wild rice particles to soften and hydrate if you’re using freshly ground wild rice.
To cook the crepes, grease an 8 inch nonstick pan, and heat until gently smoking. Ladle scant ¼ cups of batter into the pan, swirling it to cover the bottom of the pan, then cook on one side only, until you can see browning around the edges, which will only take a few moments once the pan gets up to temperature.
Fill each crepe with 2 tablespoons of the cheese filling, then fold up into rectangular packets, storing them seam down. From here the crepes can be stored ahead of time, and is how I prepped them for restaurant service.
To serve, brown the crepes gently in the butter until hot throughout. Meanwhile, saute the apples quickly and toss with the walnuts. Serve the crepes sprinkled with apples and walnuts drizzle the gastrique over each portion, or pass on the side.