Basic Butter Cookie

2 cups all-purpose flour

1/2 tsp baking powder

1/2 tsp salt

3/4 cup unsalted butter, softened

1 cup sugar

1 large egg

1/2 tsp vanilla

½ cup chocolate, melted

Whisk together flour, baking powder, and salt in a small bowl.

Beat together butter and sugar in a large bowl with an electric mixer at medium-high speed until pale and fluffy, about 3 minutes in a standing mixer.

Beat in egg and vanilla.

Reduce speed to low, then add flour mixture and mix until just combined.

Form dough into a 12-inch log (2 inches in diameter) on a sheet of plastic wrap and roll up dough in plastic wrap. Chill dough on a baking sheet until firm, at least 4 hours.

Put oven racks in upper and lower thirds of oven and preheat oven to 375°F.

Cut enough 1/8- to 1/4-inch-thick slices from log with a heavy knife to fill 2 ungreased large baking sheets, arranging slices about 1 inch apart (chill remainder of log, wrapped in plastic wrap).

Bake cookies, switching position of sheets halfway through baking, until edges are golden, 12 to 15 minutes total. Cool on sheets 3 minutes, then transfer with a metal spatula to racks to cool completely. Make more cookies with remaining dough on cooled baking sheets.

To garnish cookies with chocolate, melt the chocolate and cool slightly. Transfer to a heavy-duty sealable plastic bag and snip a 1/16-inch opening in 1 corner. Pipe chocolate evenly back and forth over cookies.

Let chocolate set before storing cookies.