Brown the butter by adding butter to a very small pan over medium heat. Melt butter and allow it to come to a boil. The butter will get frothy, then the froth will begin to subside (after about 5-7 minutes). At that point, add the sage and keep a close eye on the butter and watch for brown flecks to begin to appear in the butter. After the flecks appear, wait a minute or two longer for the liquid to develop a brown color and nutty aroma. Remove to a small dish to cool, leaving most of the brown flecks in the pan (you can strain it if desired). Set aside.
Heat a large cast iron skillet over medium-high heat and add olive oil until hot. Add shallot and sauté until fragrant, about 1-2 minutes.
Add sweet potato and toss to coat with oil. Add 1-2 tbsp of water to the skillet, then cover and allow sweet potatoes to cook down for about 10 minutes, tossing every few minutes.
Add celery, dried cranberries, and Flavor God seasoning to skillet, re-cover, and continue cooking down for about another 10 minutes or until sweet potatoes are fork tender, but not mushy. Stir every few minutes to evenly cook.
Remove skillet from heat and toss with sage brown butter before serving.