In the bowl of a food processor, add the flour, cubed butter, salt & pepper. Give it a few quick pulses until the mixture resembles pea-size crumbs. Add the cut-up cream cheese and steadily pulse until it all comes together. That should happen in less than a minute.

Place the dough in a gallon-size resealable plastic bag. Gently smooth it out with a rolling pin to form a rectangle. It helps to be sure that the air is removed from the bag before sealing and rolling.

Place the dough in the refrigerator for at least one hour or until ready to use.

For the filling, heat the butter and oil over medium-high heat in a medium-large saucepan.  Add the chopped leeks and minced garlic.  Cook and stir 3 to 4 minutes or until tender.  Add the broth and mustard; bring to a boil. Reduce heat and simmer, uncovered, for 1 minute.  Remove from the heat. Stir in diced ham, sweet peppers, peas, herbs, parsley, and salt.  Cool for 10 minutes.  Stir in the Gruyere cheese and flour.  

On a floured surface, roll one batch of Pastry Dough to a 17 x 12-inch rectangle about 1/8 inch thick.  Fold into quarters; unfold into a 15 x 10 x 1-inch baking pan.  Ease into sides and corners.  Trim to 1/2 inch beyond pan edges.  Cover and chill trimmings.

Transfer the filling to the pastry-lined baking pan.  Preheat oven to 375°F.

On a floured surface, roll the second batch of Pastry Dough to a 17 x 12-inch rectangle about 1/8 inch thick.  Trim to a 15 x 10-inch rectangle; reserve trimmings.  Fold the pastry into quarters; unfold over the filling. (Or see alternate method)  Fold edge of bottom pastry over top; pinch to seal.  Brush entire surface with egg wash.

Alternate method: Cut the 15 x 10-inch rectangle into ten 5 x 3-inch rectangles. Roll out and use the trimmings to decorate each rectangle as desired.  Using a floured wide spatula or bench scraper, transfer each rectangle onto your filling so they form neat rows.  Fold bottom edges over top and pinch to seal.  Brush entire surface with egg wash.  

Bake for 50 to 60 minutes or until filling is bubbly and crust is golden brown.  Let cool for 10 minutes; cut into 10 rectangles to serve.  If desired, partially wrap each portion with waxed paper or bakery tissue; tie with kitchen twine.  Serve warm or at room temperature (pie can sit out for up to 2 hours).  Reheat any remaining slices in a 350°F oven for 15 minutes.