For the crêpes, combine flour, milk, melted butter, herbs, eggs, 1/2 cup water and salt in a blender; pulse 10 to 15 seconds, until well mixed. Refrigerate batter for at least 1 hour.

Heat a 10-inch nonstick crêpe or sauté pan over medium-high heat. Add a teaspoon of butter or just enough to coat the bottom of the pan. Using a 1- to 2-ounce measure, add 1 to 2 ounces of batter to the center of the pan. Swirl the batter until it evenly coats the bottom of the pan.

Cook until edges just turn brown, about 1 minute. Flip and cook 20 to 30 seconds longer. Remove from pan and stack on a plate as done. Repeat until all the batter is gone, adding more butter as needed to prevent sticking. 

For the filling, heat a large sauté pan over medium heat. Add olive oil and butter. Add garlic, mushrooms, thyme and fines herbes. Stir well and cook 4 to 5 minutes until mushrooms are soft. Add sherry, with the pan off the flame, to ensure no flare ups. Return to heat and cook 2 minutes longer. Remove thyme and add salt and pepper. 

To assemble the crêpes, lay one crêpe flat on a serving plate. Spread about a tablespoon of pesto on one side of crepe. Top with some of the mushrooms and cheese, then fold over or roll up the crepe. Garnish with herbs and a drizzle of olive or truffle oil, if desired.