I based the filling on a caramelized leek and mushroom filling I saw in a cookbook, but I used onions instead of leeks because I am not sophisticated enough to care about leeks, and I added chard because I don't like mushrooms that much, and the chard takes some of the focus away from the mushrooms. If I do say so myself, it's a pretty darn good filling: creamy, flavorful, and rich-tasting. Jon is insane and adds Tabasco sauce to his.
This dinner was a bit time-consuming and involved, but I think it's a really nice, elegant looking meal. Jon was very appreciative. Of course, I served it with a salad as well. (And a ginger cake that will appear on the blog soon.)
Crepe envelopes with mushroom-chard filling
2/3 cup all-purpose flour
2/3 cup buckwheat flour
1/4 tsp salt
1 cup milk
1/3 cup water, plus extra if necessary
2 tbsp butter, melted
2 tbsp olive or vegetable oil
1 medium onion, diced
1/2 lb assorted mushrooms, sliced (I used a mix of shiitake and crimini, but that's just because the store was low on mushroom variety)
5 leaves Swiss chard, stems separated, both stems and leaves chopped
1/2 tsp salt, divided (1/4 tsp and 1/4 tsp)
zest of 1 lemon
5 leaves sage, julienned
3/4 cup yogurt
1/2 cup grated cheese (we used Gruyere, but any hard cheese would probably be good)
To make the crepes: Mix dry ingredients in one bowl and whisk the egg, milk, and 1/3 cup water together in another bowl. Whisk the wet ingredients into the dry. Whisk in melted butter. Cover bowl and refrigerate for at least an hour. Remove from refrigerator, whisk in a little more water if necessary to make an easy-to-pour batter. Make crepes by heating a crepe or nonstick pan with a flat bottom over medium heat. Pour 1/4 cup batter onto pan and turn to spread as evenly as possible. Cook until bottom is golden brown. Turn and cook a little more on the other side, so it has brown flecks as well. Repeat, and set crepes aside in a warm oven or microwave to keep them warm and pliable. (I actually made the filling first and then the crepes, so they wouldn't get too cool.)
To make filling: Saute onions in oil until very soft. Add mushrooms, chard stems, and 1/4 tsp salt, and cook until mushrooms are very soft and have given off their water. Add leaves and lemon zest, and cook until leaves are just wilted. Turn off heat and stir in sage leaves.
In a medium mixing bowl, combine yogurt, and egg. Whisk until smooth, and then stir in cheese, remaining 1/4 tsp salt, and vegetable mixture.
To assemble crepes: Spray a baking pan with nonstick spray, and preheat the oven to 350 F. Place one crepe "face"-side down (the face is the first side you cook; it's a little more attractive than the other side). Spoon some filling in the middle. Fold top and bottom over filling, then left and right sides, to make a little pouch. Place seam-side down in your baking pan. Repeat with the rest of the crepes. Bonus points if you have exactly the right amount of filling for the crepes. If you have extra crepes, you can eat them with butter and a little salt.
Bake crepes for 15 minutes or so. I'm not really sure how to tell if they're done visually, but 15 minutes worked for me.