In a 5- to 6-quart pot or Dutch oven heat oil and 2 tablespoons butter over medium-high. Add mushrooms, leek, garlic, 1 teaspoon salt, and 1/4 teaspoon black pepper. Cook 8 to 10 minutes or until tender. (Liquid will not be evaporated.) Stir in carrots, half the parsnips, the lentils, and broth. Bring to boiling; reduce heat. Simmer, covered, 25 to 30 minutes or until lentils are tender.

Meanwhile, in a 3- to 4-quart saucepan cook potatoes, cauliflower, and remaining parsnips in enough salted water to cover for 20 minutes or until potatoes are tender. Drain; return to pot. Add remaining butter, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Let stand, covered, 5 minutes. Mash; stir in sour cream.

Preheat oven to 425°F. In a small bowl stir together flour and 1/2 cup stout. Stir into lentil mixture along with remaining stout, tomato paste, and peas. Cook and stir until thickened and bubbly. Stir in herbs. Divide among eight 10- to 12-ounce casserole dishes. Place dishes on a rimmed baking sheet.

Spread or pipe on potato mixture. Bake 15 minutes or until browned and bubbly. For the shamrock detail, after baking the pies, lightly press cookie cutter into topper as a stencil and sprinkle in chopped herbs. Let stand 10 minutes. Serves 8.