Preheat oven to 375°F (190°C).
In a large skillet, heat olive oil over medium heat. Add onion and garlic, and sauté until onions are translucent.
Stir in butter and allow it to melt. Sprinkle in flour and cook, stirring, for about 1 minute.
Gradually add milk, stirring constantly, until sauce thickens. Season with salt, pepper, basil, and oregano.
In a 9x13 inch baking dish, spread a layer of the sauce.
Layer 3 lasagna noodles, a portion of shredded chicken, mozzarella cheese, ricotta cheese, and parmesan cheese.
Repeat layers, ending with sauce and a topping of mozzarella and parmesan cheese.
Cover with foil and bake for 30 minutes. Remove foil and bake for an additional 15 minutes, or until cheese is golden and bubbly.
Allow lasagna to cool for 10 minutes before serving.