Drain fat and brown drippings from pan. Put ¼ c. fat back in pan; blend in ¼ c. flour. Let bubble over low heat, stirring constantly, until mixture is light golden brown. Remove from heat. Pour remaining fat from drippings. Drain 1 (4 oz.) can mushrooms; add enough cold water to mushroom juice to make 2 c. Add drippings and mushroom liquid to browned flour and fat. Return to heat and cook, stirring constantly, until gravy thickens. Season with salt and pepper, and stir in mushrooms. (Mushroom stems and pieces may be used.) Let simmer 3 to 5 minutes.