In a medium bowl, whisk together the chicken stock, olive oil, ¼ cup Frank’s Red Hot Sauce, and ranch seasoning mix.
Place the chicken breasts into a large zip-top bag or shallow dish and pour the marinade over the chicken.
Refrigerate for at least 2 hours or overnight.
Heat the grill to medium-high heat.
Remove the chicken from the marinade and discard the marinade.
Grill the chicken breasts for 5–6 minutes per side, or until the internal temperature reaches 165°F.
Let the chicken rest for 3–4 minutes.
Melt the butter in a small bowl and whisk in the remaining hot sauce.
Brush the Buffalo butter sauce over the chicken.
Serve with blue cheese or ranch dressing.