Probably tomatoes or mushrooms for me as far as food items. For sauces I would say soy, fish, and worcestershire .
Parmesan. Always Parmesan. On salads. On bakes. On veg. On potatoes.
It’s not quite as universally fitting as mushrooms, but I love using dried tomatoes whenever it suits (for example, chopped up in rice dishes)
Miso, Marmite, MSG, and Maggi are all good.
Not all at once, though.
I have still yet to try Marmite. I really want to but I expect I’ll not like it.
Yes, it is a famously polarizing taste, but a small amount in something hefty like a ragout adds umami without adding too much of the marmite flavour. I’m vegetarian, and find it’s really handy for adding meatiness to such things.
If you try it and like it, do try marmite spaghetti.
I’m less familiar with Marmite but believe it’s like Vegemite, which I am VERY familiar with and love. If you don’t like the taste by itself, try it as a salty additive to meat pies. Not enough to make them taste like Vegemite but just a nice heavy flavour that fills out the taste. It’s great.
Knorr Liquid Seasoning. You can put it on almost anything, but it’s best with fried food. Hell, you can even put it on rice and it works. Ponzu is also great and I love using it on fish because of the citrus flavor.
There’s a fond made from mushrooms! The taste is very deep and rich and bursting with umami. You can probably find it in most bigger grocery stores.