To make the roux, stir together the heavy cream, flour, and dried milk powder until it forms a smooth paste and set it aside.
For the cream stew, heat a heavy-bottomed pot over medium-high heat and add the oil, onion, carrots, and potatoes. Saute the vegetables, constantly stirring for about 5 minutes, or until the onions start turning translucent but do not let them brown.
Add the vegetable stock, chicken, salt, pepper, and bay leaf, then turn the heat up to high to bring the liquid to a boil. Use a spoon or skimmer to remove any foam or oil that floats to the surface and continue doing so until there is no more foam.
Turn down the heat to low, partially cover the pot with a lid, and let this simmer for 15 minutes.
Par-boil the broccoli in a well-salted pot of boiling water for about a minute and then drain it and set it aside.
When the timer on the stew is up, add the mushrooms, submerge them and cook them through. This should take about a minute or two.
To temper the roux, add a few ladles of the hot liquid from the stew into your roux and use a whisk to dissolve the roux until there are no lumps.
When the mushrooms are cooked, pour the tempered roux into the stew, along with the creamed corn and stir this together. Bring the Cream Stew to a simmer to thicken the sauce, but do not let it boil.
To finish the stew, add the broccoli and heat it up.