How to Make It
In a large bowl, using an electric mixer, beat the butter until creamy. Add 3/4 cup of the sugar and beat at medium speed until fluffy. Beat in the egg yolk and vanilla. At low speed, beat in the flour and salt. Gather the dough into a ball and shape it into 2 logs, each about 1 1/2 inches in diameter. Roll the logs in the remaining 1/4 cup of sugar. Wrap in plastic and refrigerate until firm, about 1 hour.
Preheat the oven to 350°. Using a thin, sharp knife, slice the logs 1/4 inch thick. Arrange the slices on 2 large baking sheets and press a few slivers of candied orange peel in the center of each. Bake the cookies on the upper and lower racks of the oven for about 22 minutes, until golden around the edges and on the bottom; shift the pans from front to back and top to bottom halfway through baking. Let the cookies cool for 10 minutes on the baking sheets, then transfer them to wire racks to cool completely.
You can use either candied peel or candied zest for garnish, but it should be moist so it doesn't dry out while baking. To make your own candied orange zest: Blanch large strips of the zest of 1 orange and then slowly cook them in a mixture of 3/4 cup of sugar and 1/2 cup of water for an hour. You can also used crystallized ginger.
When chopping candied citrus peel or candied ginger, lightly spray or rub the blade of the knife with neutral vegetable oil to prevent sticking.