Heat 3 Tbsp of olive oil in a medium saucepan over medium heat.

Sautee onion and carrot until soft and golden (5 minutes), stirring often.

Add mushrooms and sautee until soft (5 minutes), stirring often.

Increase to medium high heat and add 1 1/2 cups chicken broth and 1 1/2 cps milk, bring to a light boil. Salt and pepper to taste and stir till dissolved.

Melt 4 Tbsp butter and stir in 3 1/2 tbsp flour.

Whisk the butter/flour mix into the gravy. Add more or less of the flour mixture depending on how thick you want the gravy. Remember it will still thicken as it cools. If it gets too thick add some more hot water or milk and return to a light boil again.