Preheat oven to 400 F. Toast pecans on a baking sheet until fragrant and browned, about 7-10 minutes, tossing halfway through. Once cool, coarsely chop pecans and set aside. Lightly crush espresso beans with a rolling pin and set aside. Line a baking sheet with parchment paper. In a double boiler, melt 6 ounces of dark chocolate over low heat until chocolate is smooth. Once completely melted, remove from heat and stir in remaining 2 ounces of chocolate. Pour chocolate onto baking sheet, spreading to 1/4 -inch thickness. Sprinkle evenly with pecans. Repeat with espresso beans and sea salt. Refrigerate, uncovered, until completely hardened. Break into rough pieces and serve. Store in airtight container in refrigerator.