Start up a large pot of boiling water. Chop the cauliflower into golfball sized chunks, removing the tough inner stem. Add a pinch of salt and the cauliflower to the boiling water, and cook for 6 to 10 minutes, or until cauliflower is fork tender.
Working in batches, place cauliflower in a clean dishcloth or cheesecloth and wring out as much moisture as possible.*
Place cauliflower and cream cheese in a food processor and puree until smooth and creamy. Cover to keep warm and set aside.
Add butter to a pan (use a light colored pan if possible so you can see the change in color) and place over low/medium heat. Melt butter, then add chopped sage leaves. Continue cooking. Butter will first bubble, then after 5 or so minutes will begin to darken. When little dark bits begin to form and the butter has darkened to the color of light caramel, remove from heat. Pour brown butter and sage over cauliflower and serve immediately.
*You can also remove the moisture by placing cauliflower in a wire sieve, fitting a smaller bowl on top, and pressing the bowl down to extract the water (but I found the dishtowel method to be quickest!)