Slice the chicken breasts in half, length-wise through the middle, so you are left with two thinner cutlets. Season both sides with a light sprinkle of salt, pepper, and the cumin.
Melt butter together with the olive oil in a large skillet over medium-high heat. Add the chicken cutlets and cook for 3-4 minutes per side, until browned and just cooked through. Remove chicken to a plate and set aside.
If the skillet is very dry, add another small drizzle of olive oil, then add the onion and cook for 2-3 minutes, until beginning to soften.
Add garlic and cook for 30-60 seconds, just until fragrant, then quickly pour in the broth and lime juice. Scrape the bottom of the skillet to remove any stuck on browned bits. Bring the mixture to a simmer, then reduce heat to medium and let it bubble for 3-4 minutes, until slightly reduced.
Reduce the heat further to medium-low, then add the cream and chopped cilantro. Stir gently until the cream is incorporated, then nestle the chicken breasts back into the sauce.
Let the sauce simmer very gently for about 2 minutes to warm the chicken through. During this time, spoon the sauce generously over the chicken, and sample the sauce and season with more salt, pepper, and lime juice to taste. Serve right away with lime wedges, green onions, more cilantro, etc. sprinkled on top as optional garnishes. Enjoy!