Peel, then mince or grate garlic. Heat a medium pot over medium heat. When the pot is hot, add ½ tbsp (1 tbsp) oil, then rice and garlic. Cook, stirring often, until fragrant, 2-3 min. Add 1 ¼ cups (2 ½ cups) water and half the garlic salt. Bring to a boil over high. Once boiling, reduce heat to low. Cover and cook until rice is tender and liquid is absorbed, 12-14 min. Remove from heat. Set aside, still covered.
Meanwhile, peel, then halve carrot lengthwise. Cut into ¼-inch half-moons. Roughly chop spinach.
Heat a large non-stick pan over medium-high heat. When the pan is hot, add ½ cup (¾ cup) water, then carrots. Cook, stirring often, until water is absorbed and carrots are tender-crisp, 5-6 min. Season with salt and pepper, to taste, then transfer to a plate.
Pat chicken dry with paper towels. Cut into 1-inch pieces. Season with remaining garlic salt and pepper. Reheat the same pan over medium. When the pan is hot, add ½ tbsp (1 tbsp) oil, then chicken. Cook until golden-brown, 2-3 min per side. (NOTE: Chicken will finish cooking in the next step.)
Add curry paste to the pan with chicken. Cook, stirring often, until fragrant, 30 sec. Reduce heat to medium-low, then add tikka sauce, cream and ¼ cup (½ cup) water. Cook, stirring occasionally, until sauce thickens slightly and chicken is cooked through, 5-7 min.** Add carrots and spinach. Season with salt and pepper, then stir until spinach wilts, 1-2 min.
Fluff garlic rice with a fork. Divide rice between plates. Top with chicken tikka masala.