In a large skillet over medium heat, brown chicken in oil.
Remove chicken and set aside.
To drippings, add mushrooms and garlic; saute 2 minutes.
Stir in flour until mushrooms are coated.
Gradually add water and bouillon; cook and stir over medium heat until bubbly.
Return chicken to skillet; bring to a boil.
Reduce heat; cover and simmer for 30 minutes, stirring occasionally.
Meanwhile, slice one cucumber into thin slices; set aside.
Peel remaining cucumber; slice in half lengthwise and removeseeds.
Cut into 1 -in.chunks.
Add to skillet and simmer for 20 minutes or until chicken juices run clear.
Stir sour cream into sauce; heat through but do not boil.
Garnish with reserved cucumber slices