Preheat oven to 350°F In a saucepan, brown the green onion in oil. Add beef and cook at high heat, while breaking it. When it's cooked and liquid evaporated, add oregano, chili powder, cream cheese, stock and chives. Cook while stirring until creamy. Add salt and pepper. Set aside.
Put one tortilla in a large pie plate. Cover with 1/5 of beef mixture. Sprinkle with 1/5 of cheddar. Repeat, alternating with tortilla, meat and cheese until there is no leftover. End with the cheese.
Cover the tortilla cake with foil paper. Cook in oven for 20 minutes. Remove foil paper and keep cooking about 20 minutes. Let rest 5 minutes, then cut in slices. Serve with salsa and sour cream.