Begin by peeling and quartering the Yukon Gold potatoes. Place them in a large pot of salted water and bring to a boil over medium-high heat. Allow the potatoes to cook for 20 to 25 minutes, or until fork-tender. Drain them well, then set aside to cool slightly as you prepare the filling.

In a mixing bowl, use a potato masher or fork to mash the drained potatoes while they are still hot. Gradually mix in Greek yogurt, creating a smooth, creamy texture. Season with salt to taste and set the mashed potatoes aside.

In a large pot, heat a couple of tablespoons of olive oil over medium heat. Add the sliced shallots and sauté for about 3 to 4 minutes until they soften and become fragrant.

Stir in the chopped mushrooms and diced carrots, cooking them for 5 to 7 minutes until the mushrooms are browned and the carrots soften.

Integrate the tomato paste and flour into the cooked vegetable mixture, stirring well and cooking for about 1 minute. Slowly pour in the red wine to deglaze the pot, scraping any flavorful bits off the bottom. Gradually add the vegetable broth.

Once the gravy has thickened, remove the bay leaf and stir in the frozen peas. Ensure everything is well combined before transferring the savory filling to a baking dish.

Spread the creamy mashed potatoes evenly over the vegetable filling in the baking dish, using a fork to create peaks and ridges.

Preheat your oven to 350°F (175°C). Bake the assembled Vegetarian Shepherd’s Pie for 15 minutes, then switch to broil for a few additional minutes until golden.