Making sure your turkey breast is moist and tender, not at all dry, is the biggest goal. You couldn’t ask for a better friend than the set-it-and-forget-it crockpot (frees up oven space!).
Place the carrots, celery, onions, and garlic in the slow cooker. Pour in the wine and chicken broth.
In a small bowl, combine 4 tablespoons of the butter, sage, celery seed, salt, and pepper. Spread the mixture over the turkey breast and place the turkey in the slow cooker on top of the vegetables.
Cover and cook on low for 6 hours, or until the turkey is fully cooked with an internal temperature of 165 F.
Optional Broiling Step: The turkey is ready to serve at this point, though the skin will not be crispy. If you wish to crisp up the skin, just before the turkey is cooked, preheat the broiler. Transfer the turkey to a roasting or broiling pan and broil the turkey until the skin gets browned; you may need to turn the turkey breast on one side and then the other to get the most even browning. Watch it carefully so that it doesn’t burn.
Meanwhile, make the gravy. Strain the juices from the slow cooker with a strainer, discarding the solids.
Melt the remaining 2 tablespoons butter in a small saucepan over medium heat. Whisk in the cornstarch or flour and continue whisking until it turns golden brown, 1 to 2 minutes. Gradually whisk in the strained pan drippings. Bring the gravy to a boil, whisking frequently until thickened 6 to 8 minutes. Transfer to a pitcher or gravy boat
Let the turkey breast sit for 20 to 30 minutes before slicing and serving with the warm gravy.
Notes
Once the turkey comes out of the slow cooker and rests for 20 or so minutes, it is ready to slice and serve. The turkey is ready to serve at this point, though the skin will not be crispy.
If you wish to crisp up the skin, just before the turkey is finished cooking in the slow cooker, preheat the broiler. As soon as the turkey is done, transfer the turkey to a roasting or broiling pan and broil the turkey until the skin gets browned; you may need to turn the turkey breast on one side and then the other to get the most even browning. Watch it carefully so that it doesn’t burn.