In a large bowl, combine flour and salt. Cut in butter until the mixture resembles coarse crumbs. Add egg and ice water gradually, mixing until the dough comes together. Wrap in plastic wrap and refrigerate for at least 30 minutes.

Filling Preparation

Prepare the Filling

In a skillet, heat olive oil over medium heat. Add onions and sauté until caramelized, about 15 minutes. Add garlic and wild mushrooms, cooking until mushrooms are tender. Stir in thyme, salt, and pepper. Remove from heat and let cool.

Assembly

Assemble the Empanadas

Preheat the oven to 375°F (190°C). Roll out chilled dough on a floured surface to 1/8 inch thickness. Cut into circles (about 4 inches in diameter). Place a spoonful of filling in the center of each circle. Fold over and crimp edges to seal.

Baking

Bake the Empanadas

Place empanadas on a baking sheet lined with parchment paper. Bake for 25-30 minutes or until golden brown.

Dipping Sauce Preparation

Make the Truffle Mayo Dip

In a small bowl, mix mayonnaise, truffle oil, and lemon juice until smooth. Adjust seasoning as desired.