Sift together flour, baking powder, and 1/2 teaspoon salt in a large bowl. Using a pastry blender, cut in the butter until coarse crumbs form. Add in the water, a little at a time, until dough comes together. Place onto a floured work surface, knead for 30 seconds to one minute. Shape into a flat disc, wrap in plastic wrap and refrigerate for 30 minutes.
Preheat oven to 400 degrees. Spray a large baking sheet with non-stick cooking spray; set aside.
On a floured work surface, roll out dough into a 12-inch circle. Place onto the prepared baking sheet.
In a small bowl, mix together the cream cheese and horseradish. Spread onto dough leaving a border of approximately 2 inches on all sides. Top with the roast pork, scallions, and pear slices. Carefully fold the border over the edges of the filling to create a rustic crust. Place galette into preheated oven and bake for 30 - 35 minutes until cooked through and crust has browned. Immediately top pears with bleu cheese crumbles, let galette rest for 2 - 3 minutes to allow bleu cheese to begin to soften.
Meanwhile, melt the butter in a small skillet over medium-low heat. Add pecans, remaining 1/2 teaspoon salt and brown sugar, stirring until brown sugar has melted. Cook for 2 - 3 minutes, until pecans have become coated in the brown sugar mixture, stirring occasionally. Remove from heat; set aside to cool.
To serve, cut galette into 6 slices, top with brown sugared pecans and enjoy!