Prepare a 9 x 13 baking dish by buttering it on bottom and all sides. Preheat the oven to 375 degrees. Next, cook your rice. I use 1 1/2 cups of basmati rice to 2 1/4 cups of water. I add the rice/water at the same time, bring to a bowl, stir, and immediately move to a low simmer with pot covered. It typically takes about twenty minutes to cook, however, that may differ based on your altitude. I'm in Colorado :) Pull off the stove as soon as it is done.
First, slice your squash, zucchini and mushrooms. Place them in a pot with the garlic powder, kosher salt, pepper, onions and chicken broth. Cook them covered on simmer, about twenty minutes max, until everything is tender. Pull off the stove.
In a small pan, melt your butter and gradually add in your bread crumbs. We like our bread crumbs pretty crispy, so the mixture is not going to be soupy, it should clump a bit.
Finally, grab a large mixing bowl and add sour cream, grated parmesan, 2 eggs, 1/2 cup milk and mix. Next, add in your rice, squash/zucchini/mushroom/onion mix and stir. Do NOT add your bread crumb mix yet!!
Assemble your casserole! Pour the entire large squash mix into the casserole dish. Smooth it out a bit if needed using a spatula. Last step - spread the bread crumb/butter mix on top. Place in the oven uncovered and set timer to twenty minutes to check it! It should be done at about twenty-five minutes, but I always suggest checking things a bit early because every oven and climate for cooking is different. Pull it out of the oven and serve after cooling for a few minutes. This recipe is great for leftovers and reheating!