Preheat oven to 425 degrees. Place a large wire-mesh strainer (or colander) in the sink. Thoroughly rinse produce and pat dry. Remove leaves from cauliflower head, core, and cut into bite-sized florets. Bring cauliflower florets and enough water to cover to a boil over high heat. Coarsely chop sun-dried tomatoes and place in a small bowl with hot water to soak for at least 5 minutes. Mince garlic. Stem kale and coarsely chop. Rinse chicken breasts and pat dry.

Lay chicken breasts flat on cutting board and, holding a knife parallel to cutting board, make a slit 3/4 of the way through the middle, so it can be opened like a book. This is called "butterflying." Season both sides with a pinch of salt and pepper. If your chicken breasts are thinner than pictured, they'll just cook a bit faster. Don't worry - they'll still be delicious!

Once cauliflower is boiling, cook 10-12 minutes, or until cauliflower is fork tender. Strain cauliflower, return to pot over medium heat, and cook 1 minute to evaporate excess moisture. Add sour cream and mash with a potato masher or fork. Don't worry if cauliflower doesn't become perfectly smooth. Stir in red pepper flakes (start with half the packet, taste, and then add more, if desired) and 1/4 tsp. salt. Set aside.

Drain sun-dried tomatoes in a wire-mesh strainer and return to small bowl. Add pesto and combine. Open each chicken breast, scoop half the pesto-tomato filling inside each breast, then close. Heat 1 tsp. olive oil in a medium oven-safe pan over medium-high heat. Place chicken in pan and brown. Carefully flip chicken over, then place pan in oven. Roast for 7-10 minutes or until a minimum internal temperature of 165 degrees is reached. Remove from oven and set breasts on a plate to rest.

Return pan used to cook chicken (no need to wipe clean - the brown bits are full of flavor) to medium heat and add 2 tsp. olive oil. Add garlic and cook for 30 seconds, or until fragrant. Add kale and cook 5 minutes, moving greens around as they cook, until kale is tender. The pan will be overflowing at first, but kale cooks down to a fraction of its original size. Season with a pinch of salt and pepper.

Slice chicken, if desired, and place on plate. Set a scoop of cauliflower mash and kale alongside chicken.