In a large pot, combine 1 cup of chicken broth and the boneless, skinless chicken breasts. Bring to a boil over medium-high heat. Once boiling, reduce the heat to low and cover the pot. Let the chicken simmer for about 15-20 minutes, or until cooked through.
Remove the chicken from the pot and allow it to cool slightly. Once cool enough to handle, shred the chicken using two forks. Set it aside for later use.
In the same pot, add the remaining 1/2 cup of chicken broth, drained petite diced tomatoes, taco seasoning, and cayenne pepper (if using). Stir to combine and bring to a simmer.
Add the pieces of cream cheese to the pot. Stir continuously until the cream cheese has melted and incorporated into the mixture, creating a creamy base.
Add the shredded chicken and rinsed white beans to the pot. Stir until everything is well combined. If the mixture seems too thick, you can add a bit more chicken broth to reach your desired consistency.
In a small bowl, mix the cornstarch with a tablespoon of water to create a slurry. Gradually stir this slurry into the dip, allowing it to thicken. Continue to simmer for a few more minutes.
Sprinkle the shredded Mexican blend cheese over the top of the dip. Stir until the cheese is fully melted and everything is well combined. Season with salt and black pepper to taste.
Transfer the Chicken Nacho Dip to a serving dish. Garnish with finely diced Roma tomatoes, chopped cilantro, and sliced jalapeños. Serve warm with tortilla chips or fresh veggies for dipping.