In a shallow baking dish, coat the steaks in oil, salt and pepper. Rest while you prepare the rest of the recipe.
In a large pot, bring the water and kombu to a boil. Turn off the heat and stir in the bonito flakes. Let this sit for 30 minutes with no heat. Return to a boil, reduce the heat to a simmer and cook for 10 minutes. Strain the broth with a fine-mesh strainer.
Return the dashi broth to the pot and stir in the soy sauce, mirin and season with salt.
Bring a large pot of salted water to a boil for the udon noodles. Cook the noodles according to package instructions, drain, and return to the pot. Toss with the soy sauce and sesame oil.
Preheat the grill or a large skillet over high heat.
Grill the steaks for 3 to 4 minutes per side to sear, then lower the heat to medium and cook until an instant-read thermometer reaches 130°F for rare, 140°F for medium rare and 150°F for medium-well.
Transfer the grilled steak to a cutting board, let rest for 5 to 10 minutes, then slice against the grain.
Divide the noodles, dashi and steaks between bowls. Top with eggs, garlic chips, scallions and togarashi.