While the potatoes are boiling, season the steaks with salt and freshly ground black pepper and cook under the broiler to medium, about 5-6 minutes per side. Once cooked, transfer the steaks to a platter and cover with aluminum foil, allowing them to rest for about 5 minutes.
While the steak and potatoes are cooking, fill a straight-sided sauté pan or saucepot with about 1 inch of water and bring it to a boil along with a large pinch of salt. Add the green beans to the boiling salted water and cook until tender and bright green, about 3 minutes. Drain the cooked green beans and return them to their cooking pot. Add 2 tablespoons butter and the scallions to the green beans, toss them to coat, season with salt and freshly ground black pepper and reserve.
Once the poblanos are cool enough to handle, unwrap them and peel the skin off from each pepper (it should come off very easily), then remove and discard the stem and seeds. Puree the roasted peppers in a food processor or blender with 1/4 cup of beef stock and reserve.
In a medium-size saucepan over medium heat, melt the remaining 2 tablespoons butter and add the flour. Cook flour and butter for about 1 minute then whisk in the remaining beef stock, Worcestershire sauce, cumin and pureed peppers. Season with salt and freshly ground black pepper.
To serve, slice the steak into slices 1/4 inch thick and arrange them on a plate with a helping of the mashed sweet potatoes and green onion green beans. Top everything off with some of the poblano gravy and enjoy.