Heat the oil in a pan over high heat. Add half of the meat and sear for 1 minute on each side. Season with salt and pepper. Repeat the same operation with the remaining meat.
Remove the meat from the pan and place it on a serving dish.
Add the onions to the pan and cook for 4 to 5 minutes. Add the butter and mix well. Add the mushrooms, season with salt and pepper, and cook for 3 minutes. Add the flour and paprika, mix well, and cook for 2 minutes. Add the beer and Worcestershire sauce, mix again. Add the tomato paste and simmer over low heat for 7 to 8 minutes. Add the meat back to the pan, mix quickly, and remove from heat. Add the sour cream, mix well, and serve.