You can use any mushroom you prefer here, and while I like trout on the bone, you can certainly use fillets -- or pretty much any other fish you feel like. In a perfect world it would be any fish you caught in springtime, but hey, try it with whatever fish you like.
4small trout, whole or beheaded(guts and gills removed)
1 1/2cupsfine cornmeal or flour
1/2poundshiitake or other mushrooms
1cupfresh or frozen peas
1tablespoonfinely chopped parsley
1/2teaspoondried or fresh thyme
Juice of a lemon
In a large frying pan, ideally cast iron, cook the bacon over medium-low heat until crispy. Remove and cut into batons and set aside. Turn the oven to "warm" and set a wire rack over a baking sheet inside; this is to keep the trout warm.
While the bacon is cooking, salt the trout inside and out. When the bacon is done, coat the fish in fine cornmeal. Turn the heat in the pan to medium-high. When it's good and hot, fry the trout in batches until they are crispy and cooked through, about 6 to 8 minutes per side. You will likely need to lower the heat on the fish at some point -- the key is to listen: The frying trout should sound just like the bacon. A happy sizzle. When they're done, carefully move the trout to the rack in the oven. I do this with two spatulas.
Put the onions in the frying pan and saute for a few minutes, until they soften and begin to brown a little. Add the mushrooms and toss to combine. Saute until they begin to give up their water, about 3 minutes, and then jack the heat up to high. Let everything sit for a minute to get a bit of a crust, then toss to combine.
Add the peas, the bacon batons, parsley and thyme and toss to combine. Cook just until the peas are warm, about a minute. Serve all this as a bed for the trout and squeeze some lemon over everything right as you serve.
NOTE:Fine cornmeal is often sold as "fish fry," and is often in the Cajun section of the supermarket.