In a small pan, melt the butter. Once melted, add the diced mushrooms to the pan, stirring to coat in the butter. Saute for about 5 minutes, until the edges of the mushrooms are slightly browned.

While the mushrooms are cooking, add the walnuts and herbs to a food processor and pulse 4-5 times, until everything is finely chopped.

Remove the mushrooms from the heat and combine them in a bowl with the walnuts and herbs. Season with salt and pepper to taste.

Using a sharp knife, slice each turkey breast tenderloin horizontally, without slicing all of the way through.

Open each tenderloin like a book, then cover them with plastic wrap. With a heavy-bottomed pan or mallet, pound each piece until they are uniformly ¼ inch thick.

Season both sides with salt and pepper.

Evenly spread the filling over each prepared turkey breast, leaving about 1” of space at the top.

Starting at the edge closest to you, tightly roll the turkey breast away from you. Repeat with the other prepared tenderloin.

Tie each roulade with 2-3 pieces of kitchen twine crosswise to hold it together. Tuck the edges in, then use one piece of twine to tie it lengthwise.

Place the prepared roulades into an oven safe baking dish. Drizzle with the olive oil.

Roast in an oven preheated to 375 degrees for 30-35 minutes, or the roulades reach an internal temperature of 165 in the thickest part.

Remove from the oven, and allow them to rest for at least 10 minutes before slicing.