Butter and sugar 8 (6-ounce) souffle dishes, including the top edge of each dish. In a medium saucepan over high heat, combine milk and vanilla bean. Bring to a boil and remove from heat. Let seep for 1 hour. Remove bean from milk, reserving 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 bath. Add egg yolks and vanilla extract to the flour 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. Transfer to the ice bath to cool completely. Refrigerate until ready to use.
Remove souffle base from refrigerator and bring to room temperature, about 1 hour.
Adjust oven rack to the center of the oven. Preheat oven to 375 degrees F. In the bowl of an electric mixer fitted with the whisk attachment, on low speed, whip egg whites 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 3 additions. Divide between prepared dishes and 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 sponge-like, about 16 to 20 minutes. Remove from oven and dust with confectioners' sugar. Serve immediately with Vanilla Bean Ice Cream.
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