Crust: Add flour, sugar, basil, oregano and salt to a food processor and pulse until combined. In a small bowl, whisk together the egg, vinegar and water. Add cold butter to the flour mixture and pulse until you have peas sized pieces of butter. Pour water mixture over the flour and pulse just until the dough comes together. Form it into a one inch disc and wrap in plastic. Refrigerate for at least 30 minutes.
Preheat oven to 425º.
Filing: Heat butter in large skillet and add onions. Sprinkle with salt and pepper and cook until translucent, about 4-5 minutes. Add garlic and cook for 1 minute. Add potatoes and stir cooking for 10 minutes or until tender but not mashed, stirring frequently. Sprinkle the flour over the mixture and stir, cook for 2-3 minutes.
Warm chicken stock in the microwave and then slowly add to the potato mixture stirring constantly. Once combined, add corn and chicken. Stir in cream and salt and pepper. Let cool slightly.
Roll out cold crust onto a piece of parchment paper until it is 1/4 inch thick. If it is too soft to work with, place it back in the refrigerator for a few minutes. Spoon the chicken mixture into the center leaving about 2 inches around the edges. Fold edges over. Brush the crust with cream and sprinkle the crust with coarse sea salt.
Bake for 30 minutes or until the filling is bubbly and the crust is golden. Let sit for 5 minutes before serving.