Step #2 Grease a 9 by 13-inch casserole with the oil & set aside.
Step #3 Bring a large pot of water to a boil, add the carrots, & cook this until tender, about 15 mins; drain.
Step #4 Combine the carrots with the remaining ingredients in a food processor/blender & process until smooth, scraping down the sides of the bowl as necessary.
Step #5 Depending on the size of your processor, you may need to so this in batches.
Step #6 Spoon the mixture into the prepared casserole.
Step #7 Combine the brown sugar, flour, pecans, & butter in a medium bowl.
Step #8 Stir to mix.
Step #9 Scatter the mixture over the top of the casserole & bake this until the topping is lightly browned, 55 mins to 1 hr.