Step 1

Whisk together melted butter, pumpkin, sugar, and vanilla in a large mixing bowl. Whisk in eggs one at a time until smooth. Stir in flour, baking powder, salt, cinnamon, cloves, ginger, and nutmeg until incorporated. Cover dough and chill for 45 minutes.

Step 2

Preheat oven to 350°F and line two baking sheets with parchment paper. Divide dough in half and shape dough into 2 (10-by-4-inch) loaves on prepared baking sheets.

Step 3

Bake for 30 minutes, until pale golden. Carefully transfer loaves to a wire rack and cool for 15 minutes. Using a serrated knife, cut loaves into 1/2-inch slices. Place slices cut side down on baking sheets; bake 12 minutes. Turn slices over and bake for 12 minutes more or until golden. Cool completely on wire racks.

Step 4

Place white chocolate in a double boiler or in a heat-proof bowl over a saucepan of gently simmering water. Slowly melt the chocolate, stirring occasionally until glossy and smooth. Transfer chocolate to a small piping bag and drizzle over biscotti. Sprinkle with pecans and let chocolate set before serving. Store at room temperature in an airtight container.