Add the sweet potatoes to a large saucepan and add enough water so that they are just immersed. Sprinkle with salt. Bring to a boil and then lower to a simmer. Cook until tender, about 6-8 minutes. Remove from heat, drain and set aside.
In a small bowl, mash the sweet potato with a fork. Add the olive oil, yogurt, chili powder, garlic powder, onion powder and a dash of salt and pepper. Stir to combine thoroughly. Add more salt and pepper to taste. Set aside.
Preheat your oven to 425 degrees F. Line a large baking sheet with parchment paper or a silicone baking mat.
Unroll your pie crust on the prepared baking sheet. Top with the sweet potato mixture, leaving a 1 1/2 inch border, so that you can fold the ends up later on. Layer the bacon, broccoli and goat's cheese on top.
Fold the edges up around the mixture. Brush the crust with egg wash. Sprinkle the crust with a little bit of coarse sea salt. Place in the oven and bake for 25-30 minutes or until the crust is golden brown.
While your galette is baking, prepare your balsamic reduction. In a small saucepan, add the balsamic vinegar. Heat over low heat and reduce by at least half, about 8-10 minutes. You will know that the vinegar is thick enough when it coats the back of a spoon generously without dripping. Set aside.
Remove the galette from the oven and let stand for 2 minutes. Drizzle the balsamic reduction on top and sprinkle with fresh parsley.
Serve immediately and enjoy!