Mustard Green Mac and Cheese

1. Cook carrots in large saucepan of boiling salted water 5 minutes, or until tender. Drain, then transfer carrots to blender using slotted spoon. Add 2/3 cup broth to blender. Cover, and blend carrots into smooth puree. Set aside.
2. Cook macaroni in saucepan of boiling water 6 minutes, or until just tender but still firm. Drain, and set aside.
3. Coat large nonstick skillet with cooking spray. Add butter, and melt over medium-low heat. Add mustard greens, and cook 2 minutes to wilt slightly. Add 2 Tbsp. broth, cover pan, and cook 4 minutes, or until greens are tender but still bright green, stirring occasionally. Remove from heat.
4. Toss together cheese and flour in bowl. Bring remaining 1 cup broth and carrot puree to simmer in saucepan over medium heat, and gradually whisk in cheese mixture. Simmer 3 minutes, or until sauce is thick and smooth, whisking constantly. Reduce heat to low, and stir in macaroni, then mustard greens.