Bring stock and 1L of water to a boil in a large saucepan. Add pasta. Cook for 10 to 12 minutes or until tender. Drain. Rinse under cold water. Drain.
Brush corn with 1 teaspoon oil. Heat a large frying pan over medium-high heat. Cook corn for 6 to 8 minutes, turning occasionally until charred. Transfer to a plate.
Heat remaining oil in same frying pan over medium-high heat. Add bacon. Cook, stirring occasionally, for 2 to 3 minutes or until browned and crisp. Transfer to paper towel to drain.
Combine sour cream, mayonnaise, vinegar and mustard in a medium jug. Season with salt and pepper. Using a large knife, cut kernels off corn. Place pasta, chicken, bacon, corn, spinach and dressing in a large bowl. Toss to combine. Serve.