Savory Autumn Crumble

Today's recipe is some seriously autumnal stuff. It's the brainchild of an October Sunday when, after a weekend of nonstop reading and grading (oh, midterm: exactly WTF is your problem?), I was A. starving, and B. incapable of doing any more work.  The happy result was this crumble, which is like the product of a wholly unsanctified - yet passionate - union between a savory casserole and a dessert: the dish that dare not speak its name!

Savory Autumn Crumble
The Filling
Ingredients
~ 1 cup brown lentils
~ 3 cups vegetable broth
~ 1 tbsp. olive oil
~ 1 tbsp. vegan margarine (I use Earth Balance)
~ 1 big onion, diced
~ 2 large carrots, diced
~ 2 stalks celery, diced
~ 3 medium potatoes, cubed
~ 2 tbsp. minced garlic
~ 1 tsp. each: sage, marjoram, parsley
~ 1/2 tsp. each: salt, thyme, rosemary
~ Lots of black pepper
~ 10 oz. package mushrooms (about 4 cups sliced)
~ 3 medium apples, cubed
~ 1 tbsp. vegan Worcestershire sauce
~ 1 tsp. Marmite
~ 3/4 cup frozen peas
~ 2-4 tbsp. flour

Directions
~ Preheat the oven to 350 degrees fahrenheit, and coat a casserole dish with cooking spray.
~ In a saucepan, bring the stock to a boil and add the lentils. Cover, reduce to a simmer, and cook for 20-30 minutes, until the lentils are quite tender. Remove from heat and set aside. (NB the lentils will cook more quickly if you've soaked them for an hour or two beforehand.)
~ In a large, deep skillet, heat the oil and margarine and sauté the onion, celery, and carrot over medium heat for about 3 minutes.
~ Add the potatoes, garlic, and dried seasonings, and cook another 5 minutes, stirring often.
~ Add the mushrooms and apples, stir to combine, and then cover the pan and cook for 5 minutes, until the mushrooms have given off their liquid and the vegetables are getting tender.
~ Stir in the Worcestershire sauce, Marmite, frozen peas, and the lentils with whatever is left of their cooking liquid. Stir to combine, then mix in the flour. (You want enough flour to make a gravy, but not so much that the filling becomes too solid; remember, it still has to bake!)
~ Transfer the filling to your prepared casserole while you make...

The Topping
Ingredients
~ 1.5 cups flour
~ 6 tbsp. cold vegan margarine or shortening
~ 1/2 tsp. each: salt, sage, black pepper

Directions
~ In a bowl, combine the flour, salt, sage, and black pepper.
~ Chop or grate the cold margarine into the flour mixture, then rub the whole mess together with your fingers until it resemble coarse crumbs.
~ Sprinkle the crumble mixture evenly over the filling, then bake uncovered for 25-30 minutes, until the topping is crisp and golden.
~ Allow to cool briefly before serving.