Preheat oven to 350 degrees. In a large bowl, beat butter with sugar and fennel seeds on medium-high speed until light and creamy, about 3 minutes. Beat in egg until combined. Add flour, cornmeal, baking powder, and salt and beat just until combined. Stir in raisins and chocolate.
Scoop heaping tablespoons of dough (or use a 1 1/2-inch ice cream scoop) onto parchment-lined baking sheets, about 2 inches apart. Bake, rotating sheets once, until edges are golden, about 15 minutes. Let cool on sheets on wire racks at least 10 minutes before serving warm or at room temperature. Cooled completely, cookies can be stored at room temperature up to 3 days.