Butter and sugar eight 6-ounce souffle dishes, including the rim of each dish. In a medium saucepan over high heat, combine milk and vanilla bean with scrapings. Bring to a boil, and remove from heat. Cover, and let steep for 1 hour. Remove bean from milk, and reserve for another use.
In a medium bowl, combine flour, 1/3 cup granulated sugar, and salt. Add 1/2 cup steeped milk, whisking to combine and form a paste. Transfer paste to saucepan with milk, and cook over medium heat while whisking constantly until thickened and smooth, about 5 to 8 minutes. If the mixture begins to get lumpy, remove from heat, and whisk until smooth. Remove saucepan from heat.
Prepare an ice-water bath: Fill a large bowl with cold water and ice. Add egg yolks and vanilla extract to milk mixture, and whisk to combine. Transfer souffle base mixture to a shallow 1-quart container. Cover surface directly with plastic wrap to prevent a skin from forming. Set saucepan in the ice-water bath to cool completely. Refrigerate until ready to use.
Remove souffle base from refrigerator, and bring to room temperature, about 1 hour.
Preheat the oven to 375 degrees with rack in center. In the bowl of an electric mixer fitted with the whisk attachment, whip 5 egg whites on low speed with cream of tartar until foamy. Gradually add remaining 1/4 cup sugar while slowly increasing the speed of the mixer until it is on high. Whip until egg whites are stiff and shiny.
Gently fold egg whites into the souffle base in three additions. Divide between prepared dishes, gently tap on each dish on the work surface, and place on a baking sheet. Transfer to oven, and bake until dark golden and the sides appear spongelike, 16 to 20 minutes. Remove from oven, and dust with confectioners' sugar. Serve immediately with vanilla bean ice cream.