Heat 1 1⁄2 cups water to 115° in a 1-qt. saucepan over high heat. In a medium bowl, stir together the water, yeast, and 2 1⁄2 cups of the flour to form the starter. Cover with plastic wrap, let sit at room temperature until bubbly and foamy, about 4 hours, then refrigerate overnight. The starter will keep for up to 3 days.
Put fennel seeds into a bowl; pour in enough boiling water to cover. Let fennel seeds soften for 20 minutes. Drain and set aside.
Transfer reserved starter to the bowl of an electric mixer fitted with a dough hook. Add sugar and 1⁄2 cup tepid water; mix on low speed to combine. Add the remaining flour in 3 additions; mix until a dough forms, then continue to mix on low speed for 5 minutes. Add a third of the butter and mix until incorporated, about 5 minutes. Repeat with remaining butter in 2 more batches. Add fennel seeds, raisins, orange peel, and pine nuts and mix until incorporated.
Turn dough out onto a floured surface, form into a ball, and cut into 4 equal pieces. Roll each piece into a ball; divide balls between 2 parchment paper-lined baking sheets. Let rise, uncovered, in a warm place until doubled in size, 2–2 1⁄2 hours.
Heat oven to 350°. Using a razor blade, cut a triangle on top of each dough ball. Bake until golden, about 50 minutes. Let cool for 10 minutes before slicing.