Heat oil in a Dutch oven or stock pot to medium-high heat. Add onion and carrots and saute 4-5 minutes, until tender.
Add butter and stir until melted. Slowly stir in flour until coated in fat and cook for 2-3 minutes, until golden. Increase heat to high and slowly whisk in chicken broth, creating a smooth mixture. Bring to a boil, then reduce to a simmer and cook 5-6 minutes, whisking constantly, until thickened.
Add chicken and egg noodles, season generously with salt and pepper, then stir in thyme and sage, until combined. Place bay leaf on top and allow to gently simmer for 15-20 minutes.
Stir in half and half or cream. Taste and adjust seasoning, if necessary. Remove bay leaf and discard.