Preheat the oven to 400°F.

Peel the Yukon Gold and sweet potatoes and cut into 1-inch pieces. Place in a medium pot and cover by an inch with cold, salted water. Bring to a boil, then lower the heat and simmer until tender, about 15 minutes. Drain well, then return to pot and mash with 2 tablespoons of the olive oil and a few good grinds of pepper.

Heat one tablespoon of the olive oil in a wide skillet over medium heat. If you have a shallow Dutch oven or other attractive stovetop-to-oven cookware, you can use it from this point and bring it all the way to the table. Add the onion, carrot, celery, about ¾ of the chopped garlic, the ground coriander and thyme sprigs. Cook, stirring from time to time, until softened, about 10 minutes.

While the onion mixture cooks, chop the mushrooms and sun-dried tomatoes together into a rough dice. Add to the pan along with the vinegar and cook, stirring occasionally, for 10 minutes. Add the wine, turn up the heat to bring to a boil for a minute. Add the stock, lentils and chickpeas (along with some more salt if those ingredients are unsalted) and simmer briskly until the stock creates a slightly thickened sauce, 5 to 10 minutes more. Remove the thyme stems, stir in the chopped parsley and taste for salt and pepper.

Transfer to a baking dish (or don’t if you’ve used oven-proof cookware). Spread the mashed potatoes overtop, creating some texture with the back of a spoon.

Pick the rosemary needles off the stems into a small bowl. Mix in the bread crumbs, remaining chopped garlic, lemon zest and remaining tablespoon of olive oil. Sprinkle the seasoned crumbs over the mashed potatoes and slide the whole thing into the oven for 10 to 20 minutes, until hot and bubbly. Finish under the broiler for two minutes, until breadcrumbs are lightly golden.