In a large nonstick pan, heat 1 teaspoon of vegetable oil over medium high heat until very hot, add chicken and cook until golden brown, and the center is no longer pink , about 4-5 minutes per side. Transfer to a plate and keep warm.
Add remaining teaspoon of vegetable oil to pan and return to the stove, add in mushrooms, onions, and salt. Cook until golden and tender.
Reduce heat to low, add in sour cream and water, heat thoroughly but do not boil. Serve over chicken.