Preheat oven to 400ºF and line two baking sheets with parchment paper. Set aside.
Wash and rinse the lentils and potatoes. Place in a large pot with the broth, garlic, and bay leaves. Bring to a boil. Reduce heat to low and cover. Let simmer for 20-25 minutes, or until the potatoes are fork tender and the lentils are cooked through.
Once cooked, drain in a fine mesh strainer, fishing out the potatoes from the lentils. Remove the bay leave and the smashed garlic cloves, and reserve the garlic to use in the sauce.
Arrange the potatoes evenly across one of the parchment-lined baking sheets, and use the back of a large spoon to smash each one down. Sprinkle 1 cup of cooked lentils over the top of the potatoes. Drizzle them with 1/4 cup olive oil, coating all potato surfaces as evenly as possible.
Place the remaining lentils in a single layer on the second baking sheet, and drizzle with 1 tablespoon or more of olive oil, and sprinkle with cracked black pepper.
Place baking sheets in the oven, with the potatoes + lentils on the top if you are using two racks.
Roast lentils for 27-30 minutes, stirring and turning them halfway through, until they are dry and crispy.
Roast potatoes and lentils for 40-45 minutes, until potatoes are golden brown and sizzling.
While potatoes and lentils cook, make the sauce. In a medium bowl, mix the minced herbs, garlic from the lentils, olive oil, lemon, and sea salt vigorously to blend into a sauce. Set aside.
In a small bowl, mix the Greek yogurt and sea salt and set aside.
Once potatoes + lentils are roasted, top each potato with dollops of yogurt, drizzle with the herb sauce, and sprinkle generously with crispy lentils. Enjoy!