Put wet mushrooms, onions, and plant cream into a crowded pan together and you are likely to get a pale stew. That can taste fine, but it is a different supper from mushrooms with browned edges on toast.
For two servings, slice 250 g mushrooms and pat away obvious surface moisture. Heat a wide pan with a tablespoon of oil. Add the mushrooms in a fairly loose layer; work in batches if necessary. Let the first side color before stirring, then continue until the released moisture has mostly evaporated.
Add a small minced garlic clove, stir briefly, and pour in about 60 ml unsweetened oat or soy cooking cream. Check that it is suitable for savory cooking. Simmer until the mushrooms are lightly coated, then season with pepper and a little salt.
Pile onto toast and add chopped chives. A few dressed leaves beside it make a welcome contrast to the warm, soft topping.