Bring a large pot of lightly salted water to a boil. Add pasta and cook 5 to 7 minutes or until al dente; drain.
Melt butter in a large saucepan over medium-high heat. Stir in onions and garlic and cook until slightly tender. Mix in mushrooms and continue cooking 2 minutes. Place steak strips in saucepan and cook about 1 minute. Mix in consomme, wine and lemon juice. Bring to a boil.
In a small bowl, thoroughly blend flour with cold water until smooth. Reduce saucepan heat to low. While stirring constantly, slowly pour flour mixture into saucepan. Gradually return to boil while stirring rapidly until sauce is thick and smooth. Cover saucepan and continue cooking 5 minutes, stirring occasionally. Remove from heat, let cool slightly and stir in sour cream. Serve over cooked pasta.