Easy---just leave it there. The practice of letting the ground freeze hard before adding additional mulch is to prevent rodents from digging for food. And they prefer bulbs because of the high starch content for energy. But if you have a couple inches of mulch already--that's great. You may not have to add any additional mulch for winter at your location. Just because the ground freezes solid does not mean your bulbs will. Bulbs contain starches and sugars that act as natural antifreeze ingredients that enable them to withstand temperatures well below 32' F even though the ground around them is frozen solid. Here in southeast Wisconsin I spread a few pine boughs around in my lily gardens around Christmas time and depend on them to catch a little drifting snow, that's all.