Put flour, salt, pepper, and dried mustard into a gallon plastic bag or a bowl and add the beef. Toss the beef cubes all around to coat them thoroughly.

Heat 2 tablespoons of the oil in a large skillet. Sear half of the beef cubes on all sides under a medium-high heat. When they are done, set them aside and do the same with the remaining 2 tablespoons of oil and the second half of the beef cubes. When you are done, leave the drippings in the skillet for the onions. 

Cook the onions in the skillet for about 3-5 minutes, until they begin to become transparent. Add any remaining flour from the ziploc bag that did not adhere to the beef cubes and toss it into the onions for another 1-2 minutes. Remove the onions and place them in the bottom of the slow cooker. Add 1/2 cup of the beef broth to the skillet and gently stir up the crusty bits at the bottom of the pan. (That's called "deglazing." The flavorful bits will make the sauce richer and more wonderful than it would be if you left them out.) Turn off the heat and pour whatever comes out with a spatula or wooden spoon over the onions in the slow cooker. 

Add the carrots, turnips, potatoes, mushrooms, and herbs. Cover the vegetables with the beef chunks. Add the tomato paste to the remaining broth, then add the paste-fortified broth and the wine to the slow cooker. 

Close the slow cooker and cook on high for 4-6 hours.