Can you keep ingredients in deep baking dish and just use immersion blender?

Yes you can but based on my experience with immersion blenders, it's going to spray tomato soup all over the place.

I suggest you fill up the baking dish with water, set it in your kitchen sink, and then let your immersion blender rip. If you are really adventurous, add some food coloring to the water.

I suggest you wear safety glasses and to avoid wearing white.

Best of luck.

You can definitely use an immersion blender, but I’d scrape everything from the baking dish into a large saucepan, add the cream and broth, and blend it in there. The higher sides will prevent splatters.