Ale and Onion Gravy

I've shared this recipe before, in conjunction with another dish, but am posting it again on its own because A. I recommended it to accompany yesterday's shepherd's pie, B. it's an excellent gravy that deserves to be highlighted, especially with the holidays approaching, and C. it's Vegan MoFo, and I need all the posts I can get, dammit. So get yourself some good, brown ale, some red and yellow onions, and summat to pour gravy on - shepherd's pie, vegan meatballs, mashed potatoes, stuffing, your chubby little children - and get busy!

Ale and Onion Gravy
Ingredients
~ 1 tbsp. canola oil
~ 1 tbsp. margarine
~ 2 large yellow onions, diced
~ 2 large red onions, diced
~ 1 tsp. each: salt, sugar
~ 1/2 tsp. each sage, parsley, marjoram
~ A few generous grinds of black pepper
~ 2 tbsp. flour
~ 1-2 tbsp. vegetarian Worcestershire sauce
~ 1 tsp. Marmite
~ 12 oz. brown ale
~ 8 oz. vegetable stock

Directions
~ Heat the oil and margarine in a saucepan and cook the onion over medium heat for about 15 minutes, stirring frequently, until soft.
~ Turn the heat down to low, stir in the salt, sugar, sage, parsley and pepper, then leave the pan uncovered and continue cooking until the onions are brown, reduced and caramelized. Remember to give them the occasional stir so they don't stick; this should take another 20-25 minutes.
~ Add the flour, Worcestershire sauce, and Marmite; stir to make a roux, adding a bit of the stock to make a smooth paste, and cook another minute or two.
~ Gradually add the ale and the remaining stock, stirring with each addition, and bring to a simmer.
~ Cook another 10-15 minutes, stirring frequently, until slightly thickened. Serve hot.