Heat a large pot with water and bring to a boil. Once boiling, add peeled and chopped carrots to water and cook for 13-15 minutes or until fork tender. Drain.

In a saucepan over medium heat, add butter. Once mostly melted, add in onions and cook for 2-3 minutes until beginning to soften. Add in garlic and cook for 20 more seconds. Whisk in flour, salt, pepper, and celery salt. Then mix in brown mustard.

Pour milk into flour mixture and whisk until smooth. Bring to a low simmer and then add in Old English Cheese. Let cheese melt and bring to light simmer, cooking for an additional 5 minutes until sauce has thickened up.

Pour carrots into 9x13 casserole dish (or slightly smaller). Pour cheese sauce on top and mix until carrots are coated. Sprinkle top with breadcrumb and bake for 25 minutes at 350F.

Broil the last few minutes to make the breadcrumbs golden brown.

Let cool at least 20 minutes before serving.