1. Preheat oven to 350°F (180°C). Spray a 9-inch square baking pan with cooking spray. Line pan with parchment paper, letting excess extend over sides of pan. Line a rimmed baking sheet with parchment paper.

2. On prepared baking sheet, spread oats in an even layer.

3. Bake until fragrant and lightly toasted, 10 to 12 minutes, stirring occasionally. Let cool slightly on pan on a wire rack. Reduce oven temperature to 325°F (170°C).

4. In a medium heatproof bowl, place halved prunes; add ½ cup (120 grams) boiling water (prunes should be just submerged), and let stand for 15 minutes.

5. Transfer prune mixture to the work bowl of a food processor; pulse until relatively smooth, stopping to scrape sides of bowl, if necessary. (It’s OK if some flecks of prune remain.)

6. In a small saucepan, combine prune mixture, almond butter, honey, 1 tablespoon (14 grams) oil, and kosher salt; cook over medium-low heat, stirring occasionally, until oil is melted and mixture is well combined. Remove from heat; stir in vanilla bean paste and orange zest.

7. In a large bowl, stir together toasted oats, chopped prunes, roughly chopped pistachios, sesame seeds, and pumpkin seeds; use hands to break up any large prune clusters, if necessary. Stir in prune mixture until well combined.

8. Transfer oat mixture to prepared 9-inch pan. Using a sheet of plastic wrap, press into an even layer.

9. Bake until fragrant, edges feel lightly toasted, and top feels mostly dry, 20 to 25 minutes. Let cool completely in pan on a wire rack.

9. In the top of a double boiler, combine chocolate and remaining 2½ tablespoons (35 grams) oil. Cook over simmering water, stirring frequently, until melted and smooth. Working quickly, pour chocolate mixture over cooled oat mixture. Tilt pan as needed to spread chocolate mixture into an even layer; tap pan on a kitchen towel-lined counter several times to smooth chocolate mixture and release any air bubbles. Sprinkle with finely chopped pistachios. Refrigerate, uncovered, for at least 1 hour or up to overnight.

10. Using excess parchment as handles, remove from pan. Using a warm, dry serrated knife, trim edges, and cut into bars. Garnish with sea salt, if desired.