Toast the pine nuts in a small, dry pan until lightly browned and fragrant. Pour them onto a plate or cutting board to cool. Set aside.
In a medium saucepan with a lid, combine the stock, 1 tablespoon of the oil, mustard, tomato paste, sumac, and salt and pepper to taste. (This liquid must taste very flavorful. The rice will absorb it.) Bring it to a simmer. Taste and adjust any seasonings as desired.
Add the rice and stir. Place the lid onto the saucepan and reduce the heat to low.
Cook the rice for 15 to 20 minutes, or until the liquid has been absorbed.
While the rice is cooking, in a medium skillet or frying pan, heat the remaining tablespoon of the oil over medium-low heat. Once hot, add the leeks and shallot. Sprinkle lightly with salt and pepper. Stir.
Sauté the vegetables, stirring often, until they are beginning to soften.
Add the garlic and stir for about 20 seconds. Lower the heat if the veggies are browning.
Turn off the heat and add the artichokes, capers, oregano, and parsley. Stir to combine and heat through. Turn off the heat; the vegetables will keep warm.
After the rice has cooked, pull the pot off the heat. Leave the lid on the pot and allow it to sit for 5 minutes.
After 5 minutes, fluff gently with a fork.
Pour the fluffed rice into the warm vegetables. Gently toss to combine. Serve from the saucepan or pour into a serving bowl. Sprinkle with the toasted pine nuts.
Serve warm.