Cook the sweet potatoes until very tender. Bake them at 400°F for about 45–60 minutes, or peel, cube, and boil them until soft. Cool, mash until smooth, and measure 2 cups.

Heat the oven to 350°F and thoroughly grease and flour a 10- to 12-cup Bundt pan.

Whisk the flour, baking powder, baking soda, cinnamon, nutmeg, ginger, and salt together in a bowl.

Beat the softened butter and sugar for 3–4 minutes, until light and fluffy. Add the eggs one at a time, beating well after each addition, then mix in the sweet potato and vanilla.

Add the dry ingredients in three additions, alternating with the buttermilk in two additions. Mix only until combined, then fold in nuts if using.

Transfer the batter to the prepared pan and smooth the top. Bake for 55–65 minutes, until a toothpick inserted in the thickest part comes out clean or with a few moist crumbs.

Cool the cake in the pan for 10–15 minutes, then invert it onto a rack. Cool completely before glazing.

Whisk the confectioners’ sugar, milk or orange juice, vanilla, and salt until smooth. Add the liquid gradually so the glaze remains thick but pourable, then drizzle it over the cooled cake.