Heat the oven to 350ºF.

• Trim the root ends of the leeks. Cut lengthwise and then into ¼-inch-thick half-moon pieces. In a bowl of water, soak the leeks, allowing any dirt to settle at the bottom.
• Rinse the chard, strip the leaves from the stems, then coarsely chop the leaves and stems, keeping them separate.
• Crush the garlic.

• In a strainer, rinse the rice and lentils under cool water.

In a pot over medium heat, warm 2 tablespoons oil until hot but not smoking. Lift the leeks from the bowl, making sure not to add any of the dirt that’s collected at the bottom. Add the leeks to the pan, season with salt, and cook until just starting to soften, 3 to 4 minutes.
Add the mujadara spice blend and toast until just fragrant, 20 to 30 seconds. Add the chard stems, rice, and lentils. Season with salt and pepper, and cook, stirring occasionally, until toasted, 2 to 3 minutes. Add 3 cups of water and the bay leaf. Increase the heat and bring to a boil.
Reduce to a simmer, cover, and cook until the rice and lentils are tender, 22 to 24 minutes. Add the chard leaves and cook, stirring, until just wilted, 30 seconds to 1 minute. Season to taste with salt.
While the rice and lentils cook, make the garlic flatbread.

On a sheet pan, rub the flatbread with the garlic, drizzle with oil, and season with salt. Bake until lightly toasted and crisp, 15 to 17 minutes. Let cool slightly and break into large pieces.

Discard the bay leaf and transfer the mujadara to individual bowls. Top with yogurt, garnish with the sumac and crispy shallots, and serve with the flatbread on the side.