We do not advocate smoking in an oven or ever adding liquid smoke. One safety first, two the other has a distinct flavor that isn't the same as charcoal or even pellets add when smoking. Now, there are some options though: If you have a smoking gun, consider smoking the beer for a minute before making the roux with it. Alternatively, swap out the Dubliner and cheddar cheese for smoked cheese to work the nuance of flavor in. Just make sure it's a good melting cheese like Gouda.