So, two things here, it will seem like the mixture is really thick and like there's not enough batter, and, it's OK if there are lumps. The thing is, there are lots of bits of bacon and cheese, so it's really heavy on the mix-ins, but the proportions are right, and given that fact, there will definitely be lumps. Just don't over mix the batter and all will be well!
Spoon into a paper-lined muffin tin and bake for 15-20 minutes. I recommend you let these cool a bit before eating since the papers won't stick as much.