PreparationFor candied orange peel: Using a sharp knife, cut all rind and white pith from oranges in wide strips. Trim off any flesh still clinging to the white pith. Place peel in a small heavy saucepan. Add cold water to cover; bring to a boil. Drain. Repeat with cold water. Drain; reserve peel. Combine sugar and 2 cups water in same saucepan. Stir over medium heat until sugar dissolves. Add the orange peel, star anise, and vanilla bean. Bring to a boil. Reduce heat to low and simmer, partially covered and stirring occasionally, until peel is soft and syrup has thickened, 50-60 minutes. Let cool slightly. Transfer peel to a cutting board and thinly slice. Return peel to syrup. DO AHEAD: Can be made 1 week ahead. Place in a jar, cover, and chill. For cake: Preheat oven to 350°F. Butter pan. Line with a parchment-paper round; butter paper. Bring currants and Grand Marnier to a simmer in a small saucepan over medium heat. Remove from heat and let steep. Meanwhile, sift flour, baking powder, and salt into a medium bowl. Using an electric mixer, beat 10 tablespoons butter and sugar in a large bowl until light and fluffy, about 3 minutes. Beat in orange juice, marmalade, and orange zest. Beat in eggs one at a time, blending well between additions (mixture may look curdled). Add dry ingredients in 3 additions and milk in 2 additions, beginning and ending with dry ingredients and beating to blend between additions. Beat in any Grand Marnier not absorbed by the currants. Fold in currants. Pour batter into prepared pan; smooth the top. Bake cake until a tester inserted into the center comes out clean and the top is golden, 40-45 minutes. Let cool in pan on a wire rack. DO AHEAD: Can be made 1 day ahead. Store airtight at room temperature. Remove pan sides from cake. Invert onto a serving plate. Arrange candied orange peel over and brush with some of syrup, if desired.
PreparationFor candied orange peel: Using a sharp knife, cut all rind and white pith from oranges in wide strips. Trim off any flesh still clinging to the white pith. Place peel in a small heavy saucepan. Add cold water to cover; bring to a boil. Drain. Repeat with cold water. Drain; reserve peel. Combine sugar and 2 cups water in same saucepan. Stir over medium heat until sugar dissolves. Add the orange peel, star anise, and vanilla bean. Bring to a boil. Reduce heat to low and simmer, partially covered and stirring occasionally, until peel is soft and syrup has thickened, 50-60 minutes. Let cool slightly. Transfer peel to a cutting board and thinly slice. Return peel to syrup. DO AHEAD: Can be made 1 week ahead. Place in a jar, cover, and chill. For cake: Preheat oven to 350°F. Butter pan. Line with a parchment-paper round; butter paper. Bring currants and Grand Marnier to a simmer in a small saucepan over medium heat. Remove from heat and let steep. Meanwhile, sift flour, baking powder, and salt into a medium bowl. Using an electric mixer, beat 10 tablespoons butter and sugar in a large bowl until light and fluffy, about 3 minutes. Beat in orange juice, marmalade, and orange zest. Beat in eggs one at a time, blending well between additions (mixture may look curdled). Add dry ingredients in 3 additions and milk in 2 additions, beginning and ending with dry ingredients and beating to blend between additions. Beat in any Grand Marnier not absorbed by the currants. Fold in currants. Pour batter into prepared pan; smooth the top. Bake cake until a tester inserted into the center comes out clean and the top is golden, 40-45 minutes. Let cool in pan on a wire rack. DO AHEAD: Can be made 1 day ahead. Store airtight at room temperature. Remove pan sides from cake. Invert onto a serving plate. Arrange candied orange peel over and brush with some of syrup, if desired.