To prepare the lamb, preheat the oven to 250°F.

In a Dutch oven over medium-high heat, warm the olive oil. Add the lamb and sear until browned on both sides. Transfer to a plate. 

Add the onions to the pot and cook, stirring occasionally, until starting to soften, about 5 minutes. Add the rosemary, thyme, salt and pepper and cook, stirring occasionally, until fragrant, about 2 minutes. Add the wine and deglaze the pot, stirring to scrape up the browned bits. Add the stock and pomegranate juice, then the lamb and any accumulated juices. Cover the pot, transfer to the oven and cook until the meat is very tender, about 5 hours. 

Transfer the lamb to a large bowl. Strain the cooking liquid through a fine-mesh strainer into a saucepan, discarding the solids. Place the pan over medium-high heat and simmer until the sauce is reduced by one-third and then whisk in the roux. Bring to a boil and then pour over the lamb. Shred the lamb, removing any unwanted fat from the meat, and refrigerate for 2 hours. 

To prepare the acorn squash, preheat the oven to 400°F. 

Cut the acorn squash in half and scoop out and discard the seeds. Season the cavities with the olive oil, rosemary, salt and black pepper. Place the squash, cut side down, on a baking sheet and roast for 15 minutes. Turn the squash over and roast until golden brown and tender, about 15 minutes more. Let cool in the refrigerator.

To prepare the fried leeks, in a pot, heat some oil. 

Trim the root end from the leek and cut off the green top. Cut the white portion of the leek in half lengthwise and place the halves in a bowl of cold water for a couple of minutes to remove any sand. Remove the leek from the water, pat dry and cut into fine julienne strips.

Put the flour in a paper bag. Add the leek strips to the bag and shake well. Transfer to a fine-mesh strainer and shake to remove the excess flour. 

Add the leek strips to the hot oil and fry until golden brown. Using a skimmer, transfer the leek strips to a paper towel–lined plate and season to taste with salt and pepper.

To prepare the herbed yogurt, in a blender, combine the yogurt, sour cream, lemon juice, parsley, salt and black pepper and puree until smooth. Add a little water if the mixture is too thick.

To prepare the pomegranate glaze, in a saucepan over medium heat, combine the vinegar, pomegranate juice, rosemary and brown sugar and simmer until reduced by half. Strain the mixture through a fine-mesh strainer, then refrigerate until cool.

To prepare the empanada dough, in a large bowl, stir together the flour and salt. Add the beef fat and margarine and mix by hand until well incorporated. Slowly add the water and continue mixing until a ball forms. 

Turn the dough out onto a work surface and knead the dough ball until smooth. Shape the dough into a log, transfer to a plastic bag and let rest for 10 minutes. Cut the dough into 1/2-inch-thick slices. Roll out each slice thinly and cut with a 3-inch round cutter.

Shape the rounds of dough by using your fingers and pinching the dough around the outside of the round and pulling to create a wall around the edges of the open empanada. Store the shells in a cool place until you are ready to fill them.

Preheat the oven to 375°F.

To assemble the empanadas, place 10 g of acorn squash and 20 g of lamb inside each dough round. Add the pomegranate glaze, herbed yogurt, fried leek strips and pomegranate seeds. Place on a baking sheet and bake until golden brown.