Make the Crepes:

1. Blend the Batter: In a blender or mixing bowl, combine flour, eggs, milk, water, melted butter, and salt. Blend or whisk until smooth. Let the batter rest for 15-20 minutes.
2. Cook the Crepes: Heat a non-stick skillet or crepe pan over medium heat. Lightly grease with butter or oil. Pour ¼ cup of batter into the pan, swirling to spread evenly. Cook for 1-2 minutes until the edges lift easily, then flip and cook for another 30 seconds. Repeat with the remaining batter.

Prepare the Mushroom Filling:

3. Sauté Onions and Garlic: In a large skillet, heat olive oil or butter over medium heat. Add chopped onions and cook until translucent, about 3 minutes. Add minced garlic and sauté for another minute.
4. Cook the Mushrooms: Add sliced mushrooms to the skillet and cook until softened and golden brown, about 8-10 minutes. Season with salt, pepper, and thyme.
5. Make the Sauce: Stir in the heavy cream and Parmesan cheese. Cook for 2-3 minutes until the sauce thickens slightly. Adjust seasoning if needed.

Assemble the Crepes:

6. Fill the Crepes: Place a spoonful of the mushroom filling onto the center of each crepe. Fold the crepes into quarters or roll them up, depending on your preference.
7. Warm the Assembled Crepes: Place the filled crepes in a baking dish, cover with foil, and warm in a 350°F (175°C) oven for 10 minutes before serving.

Garnish and Serve:

8. Add Final Touches: Sprinkle with fresh parsley and additional Parmesan cheese, if desired.