Brown the Pork
In a small skillet, brown the ground pork
Prepare the Mushroom Filling
In a large skillet, heat 2 Tbsp olive oil. Add mushrooms, sherry, soy sauce, and season with salt & pepper.
Cover and cook over medium heat, stirring a few times, until the mushrooms have released their liquid and are tender (~ 8-10 minutes)
Uncover and cook 5 or 6 minutes longer, stirring occasionally, until they're browned
In a small skillet, heat 2 tsp olive oil. Add garlic, lemongrass, chile, shallots, and 1 Tbsp ginger.
Cook over low heat, stirring occasionally, until the vegetables are golden brown, (~ 6-7) minutes.
Add the lemon zest (or juice, if using), then stir the mixture into the mushrooms, along with the browned pork
Prepare the Creamy Ginger Sauce
In a blender, puree the Greek yogurt, olive oil, tarragon, lime juice, vinegar, and the remaining 1 ½ tsp ginger, until smooth. Season with salt and pepper.
Assemble and Bake the Rolls
Preheat the oven to 400° F.
Place an egg roll wrapper on your work surface with one corner pointing at you. Add 2-3 tablespoons of filling into a 2×4-inch rectangle just below the horizontal diagonal line that connects the right and left corners. Take the corner nearest you and fold it over the filling, rolling it away from you so that the filling is completely encased in the wrapper. Fold the right and left corners in toward the center, keeping it snug, but not so tight that the wrapper breaks, and continue rolling until you have 2-inches of the last corner left.
Paint the edges of the last corner with a bit of egg, then quickly roll up the egg roll. (this will help hold it together). Lightly brush the top of the roll with beaten egg.
Repeat with the remaining wrappers and filling.
Bake for 8-10 minutes, until they're beginning to brown. Then flip them over and bake another 8-10 minutes.
(For added crispness, put the egg rolls under the broiler for 1-2 minutes, checking every 20-30 seconds)
Cut the rolls in half on the diagonal, wrap them in lettuce leaves and serve with the ginger sauce.