So, not only does this recipe veganize the classic, but it takes us back to a more whole foods version that may actually be more traditional than the versions made from canned goods. Note that I do not blanch the broccoli, but if you wanted to, go for it.
For the Seitan:
3/4 cups vital wheat gluten flour
1/4 cup Garbanzo bean flour (AKA chickpea four or Besan)
1 Tablespoon No chicken broth powder
1 teaspoon soy sauce
Up to 1 cup of filtered water
Stir everything but the water together. Start adding the water, putting in about 1/2 a cup. I find that this recipe needs a different amount of water than the recipe calls for (the original link is above), and this might have to do with the brand of vital wheat gluten flour and other factors. You want a slightly wet dough, but not so soft that you can't knead it to develop the gluten. Knead it fairly well, until you see it is forming strings. I tend to punch it in the bowl to get a cohesive mass as possible without layers caused in the kneading process.
In a standard loaf pan, put 1 1/2 cups of water, 1 teaspoon of no-chicken broth, and 1 Tablespoon of soy sauce. Place your flat oval of kneaded seitan in the broth mixture, cover the pan with foil and bake for one hour at 325. At the end of an hour, uncover, flip the loaf, and bake covered for another hour. Remove and let cool (you can make this the day before).
Combine 1/4 cup of flour of your choice with 1/2 teaspoon garlic powder, 1/2 teaspoon of onion powder, salt and pepper. Dredge the seitan cutlets in this flour mixture. In a non-stick skillet brown those pieces. Your goal here is to add a bit of texture on the outside, as well as some seasoning. This also helps to dry the seitan out a bit--it is going to bake on top of broccoli that will release a bit of moisture and under your béchamel. So, you want to dry it a bit--that's my theory, at any rate. I'm sure it would be fine if you skipped this step.
Take your broccoli and cut into florets. Spray or lightly oil a casserole dish and place broccoli in the bottom. I tossed mine with a little salt, pepper, and 1/2 teaspoon each of onion and garlic powder. Place the sliced seitan on top.
Scatter sliced almonds on top, cover the pan with foil, and bake at 375 for 25 minutes. Remove foil and bake another five minutes to ensure the almonds have a bit of crunch, if that's your thing.
Variations: You could use cheese here, and there are plenty of vegans who whip out the Daiya for this one. Gluten intolerant? I would think that Soy Curls would work well here. I would reconstitute those, squeeze out the excess water and toss them with some of the No Chicken broth powder or seasoned salt before putting them in the casserole dish. Tofu cutlets would probably work fine, as would Tempeh cutlets that are browned prior to assembly.
In a hurry or scared to make your own seitan? I would think this would work great with those store bought "Chik" patties or with Gardein chicken style cutlets. If you are wanting this quicker than the process above, use store bought unsweetened plant milk (I'd go almond, just because you have almonds on top, but that's me), Chik patties, and frozen broccoli instead of fresh.