In a medium sized bowl, season the beef cubes with 1 teaspoon salt and ½ teaspoon black pepper, then toss them in the flour until evenly coated.
Heat the olive oil in a large skillet over medium-high heat. Sear the beef in batches until browned on all sides, about 2-3 minutes per side. Transfer the beef to the slow cooker.
To the slow cooker, add the onion, carrot, mushrooms, garlic, tomato paste, diced tomatoes with juice, beef broth, red wine, Italian seasoning, and bay leaves. Stir to combine.
Cover and cook on low for 8 hours or on high for 4 hours, until the beef is tender and the vegetables are cooked through.
About 30 minutes before the stew is done, make the dumplings. In a medium bowl, whisk together the flour, baking powder, and salt. Cut in the cold butter using a pastry cutter or your fingers until the mixture resembles coarse crumbs. Stir in the milk until a soft dough forms.
Drop spoonfuls of the dumpling dough onto the surface of the stew, leaving space between each dumpling. Cover the slow cooker and cook on high for 25-30 minutes, or until the dumplings are puffed up and cooked through.
Remove the bay leaves before serving. Serve the stew hot with the dumplings on top. Enjoy!