Place the pine nuts on a sheet pan and toast until golden, 3 to 5 minutes. Set aside and leave oven on.
Bring beef stock to a simmer in a small saucepan. Add the butter and stir in the couscous. Cover the pot and remove from the heat. Let sit for 5 to 10 minutes. Fluff the couscous with a fork and place into a medium bowl. Stir in the toasted pine nuts, lemon zest and juice, tomatoes, 1 tablespoon of the chopped mint, chorizo, feta cheese and all but 3 tablespoons of the cucumber. Add salt and pepper to taste. Cover and set aside to cool.
In a small bowl combine the cumin, olive oil, salt and pepper, to taste. Brush all sides of the lamb loin with the flavored oil.
Heat a saute pan big enough to hold the loin, brush with oil. Place the loin in the pan and cook, turning until seared on all sides, about 2 minutes per side. Transfer to a sheet pan to finish cooking in the oven, about 5 minutes.
Garnish with Yogurt Sauce and Fresh Mint.
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