In a small saucepan, bring three cups of vegetable broth to a boil. Add wild rice, reduce to a medium-low boil/simmer, and cover with a loose-fitting lid. If you can tilt the lid up slightly, so that it lets some steam out, that will help the rice cook. Cook according to package instructions. Some varieties may only take 20-25 minutes, others take 40-50 minutes.
While the rice is cooking, heat oil over medium heat. Add onion and saute for 3 to 5 minutes. Add mushrooms and cook down for ~10 minutes. You may want to add a splash of vegetable stock for more flavor. Next, add the cranberries and cook for another 5 minutes or until they begin to "pop." Stir in the fresh sage.
When the rice is finished, drain the excess liquid and add it to the mushroom/cranberry mixture. You can heat it up in the same skillet or in a serving dish in the microwave, or serve cold. Serve with more fresh sage, salt, and pepper to taste.
To reduce cooking time, soak wild rice in a bowl with cold water overnight or for 3-4 hours before cooking.
You can also prep the wild rice in a slow cooker to save time. Add the rice and stock, cover, and cook on high for 3-4 hours.
You can make this ahead of time and serve cold or reheated (in the microwave for 2-3 minutes or in a preheated oven for 10-15 minutes).
Store leftovers in an airtight container in the fridge for 3-5 days.