In another baking dish I poured enough oil to cover the bottom, then mixed in some dry basil and garlic powder. Into that I tossed a bag of frozen cauli, and tossed to coat. S&P lightly.
Both of the above went into a 350 oven.
On the stovetop I put 2 drained cans of sliced shitake mushrooms into a pan with 2T butter (not fake oleo stuff), covered it, and set it on the oven-vent burner. (I don't keep fresh mushrooms because they spoil so quickly; I buy them specially if I have an immediate use for them, but keep canned and dried 'shrooms on hand.)
After 30 minutes I tossed the cauli and returned it to the oven. Then to the mushrooms (with now-melted butter) I added 8 oz of sour cream - full fat of course - a tsp of chili powder, and tsp of beef base, and a generous shake of dry basil. I stirred it all together, re-covered it, and put it on the burner set to its lowest setting.
10 minutes later I removed the meat loaf and roasted cauli from the oven, turned the burner off, and stirred the sour cream/mushroom sauce. I served it over the meatloaf. The cauli was plenty flavorful to stand on its own. The mushroom sauce had a good strong flavor - if I wanted it milder (I didn't) I would have added some cream and used just a half-tsp of the chili powder.