Preheat the oven to 350 degrees F. Lightly grease a 10-inch bundt bake pan, then flour, shaking to knock out any excess flour.

In a large bowl fitted with an electric mixer, cream the butter on medium speed. Add the sugar and beat until pale and frothy, about 3 minutes. Add the eggs 1 at a time, beating well after the addition of each and scraping down the sides of the bowl. Add 1 tablespoon of liqueur and beat to incorporate.

Into a medium bowl, sift together the flour, baking powder, and salt.

With the mixer on low speed, alternately add the dry ingredients and milk, mixing well after the last addition.

Pour 1/3 of the batter into a separate bowl and add the sifted cocoa powder, mixing well.

Pour half of the white batter into the prepared pan, spreading around the entire bottom of the pan, and top with the chocolate batter, smoothing slightly to make an even layer. Drop and spread the remaining white batter over the top. With a thin knife or skewer, swirl the 2 batters together to create a marbleized effect. Bake until the cake is set and a tester inserted into the middle comes out clean, 55 minutes to 1 hour and 5 minutes.

Remove from the oven and let the cake cool in the pan for 20 minutes. Turn out onto a wire rack with a sheet pan positioned underneath.

To make the glaze, in a bowl, combine the remaining 1/4 cup liqueur with the confectioners' sugar and 1 tablespoon milk or water and whisk until smooth, adding up to another tablespoon of liquid, as needed.

While the cake is still warm on the rack with the sheet pan underneath, drizzle the glaze evenly over the top. Sprinkle the top immediately with chopped nuts and let the glaze set and the cake cool before serving.