Remove stems from figs and chop roughly, then simmer in water for 5 minutes to soften; drain and cool. Add figs, dates, raisins, walnuts, candied orange peel, honey, orange juice, spices, and chocolate to a food processor and pulse 20–30 times until a thick, textured paste forms.
Taste and adjust the filling for sweetness or spice, then transfer to an airtight container, press plastic wrap directly onto the surface, and refrigerate until needed (up to 5 days).
Combine flour, sugar, baking powder, and salt in a food processor; pulse to mix, then add cold butter cubes and pulse until the mixture resembles coarse crumbs. Whisk together eggs, milk, and vanilla, then add to the flour mixture and pulse just until the dough comes together.
Divide the dough into 4 equal disks, wrap each tightly in plastic wrap, and refrigerate for at least 2 hours or overnight.
Preheat the oven to 375°F (190°C) and line two baking sheets with parchment paper. Lightly flour a clean work surface.
Roll one chilled dough disk into a 10–12-inch rectangle about 1/8–1/4 inch thick, then cut into 3–3.5-inch-wide strips. Spoon a finger-width log of fig filling down the center of each strip, fold the dough over the filling, and press the seam firmly to seal.
Cut each filled log crosswise into 1–1.5-inch cookies and arrange seam-side down on the prepared baking sheets with 1 inch of space between. Optionally make 2–3 shallow diagonal slits on top of each cookie.
Bake for 10–14 minutes, rotating pans halfway through, until the bottoms are lightly golden and the tops look set but still pale. Rest on the pan for 5 minutes, then transfer to a wire rack to cool completely.
Sift powdered sugar into a bowl, add 2 tablespoons of lemon juice, and stir until a smooth, spoonable glaze forms; adjust consistency with more lemon juice or powdered sugar as needed.
Brush or spoon glaze over each fully cooled cookie, immediately scatter nonpareils on top, then let stand 30–60 minutes until the glaze is completely set before serving or storing.