Step 1

Using a frying pan or a wok, put the butter, 2 tablespoons of the oil, the onions, celery and carrots in the pan and sautée over medium heat until the vegetables have wilted, about 8 minutes. Add the garlic and shiitake mushrooms for another 2 minutes more, stirring while they cook.

Step 2

Meanwhile, heat the remaining oil in a skillet until it is near the smoking point. Slip the steaks the oil and brown on all sides.

Step 3

Add the vegetables, wine, hot stock, steaks and any remaining ingredients to the slow cooker, stir well, season to taste and cook on low for 12 hours. Do ensure that the steaks are covered during the cooking.