Prep the ingredients per the instructions above.
Place the cucumber slices in the water to infuse it. Let sit in the refrigerator until ready to serve, at least 15 minutes.
Cook the rice according to the instructions on the package.
Trim most of the visible fat from the lamb then cut the meat into 1 ½” - 2” chunks. Pat down the lamb to remove any excess moisture. Then heat the oil in a pot over medium-high heat and brown the lamb on all sides.
Add the leeks, scallions, and celery to the pot and sauté until the vegetables soften. Add the chicken broth to cover the mixture and season it generously with salt and pepper. Cover and bring to a simmer for about 30 to 40 minutes.
Add the spinach and dill to the pot. Reduce the heat and simmer until the lamb is fork-tender and a small amount of liquid remains in the pot (about 3/4 cup). Turn off the heat.
Prepare the sauce: In a small bowl whisk the egg white with the cold water and cornstarch until very frothy. Whisk in the egg yolk and lemon juice. Temper the sauce by slowly adding the hot liquid from the pot to the small bowl with the eggs while whisking constantly until the egg is tempered. Now add the mixture to the pot and stir gently to incorporate and ensure everything is thoroughly mixed together.
Finish the rice: Once tender, fluff with a fork and season with salt and pepper to taste.
Portion the lamb fricassée, and serve with rice, pita, and cucumber water. Garnish with some chopped dill.