Preheat the oven to 400 degrees F. Lightly grease a 9-inch square or 2.2 quart baking dish with the butter and set aside.
In a large saute pan or skillet, heat the oil over medium-high heat. Add the onions, carrots, Essence, salt, and pepper and cook, stirring, until the onions are soft, about 3 minutes. Add the garlic and cook, stirring, for 20 seconds. Add the mushrooms, thyme, and bay leaf and cook, stirring, until the mushrooms are soft, 3 to 4 minutes. Add the flour and cook, stirring, until thick, about 1 minute. Stir in the tomato paste and cook, stirring, for 1 minute. Add the meat and stir well to combine. Gradually add the stock and then the peas, and bring to a boil. Reduce the heat to medium-low and simmer until the mixture is thickened, 6 to 8 minutes.
Remove from the heat and discard the bay leaf. Carefully transfer to the prepared dish and spoon the potatoes over the meat mixture, spreading to the edges. Sprinkle with the cheese and bake until the cheese is bubbly and the potatoes are crisp around the edges, 22 to 25 minutes.
Let sit for 10 minutes before serving. Garnish with chopped parsley and serve.