Preheat the oven 350°F (175°C). Line an 81⁄2 x 5–inch (22 x 13–cm) bread pan with parchment paper.

To make the brownies, place the hazelnuts on a rimmed baking sheet and toast for 10 to 15 minutes. Remove the sheet from the oven and allow the nuts to cool. Rub the hazelnuts in a kitchen towel to remove all the skins.

Place the cooled, skinless hazelnuts, walnuts, macadamia nuts, vanilla, honey, powdered sugar, cocoa powder and salt in a food processor. Process for about 15 seconds, stop and wipe the sides down, then process again just until the mixture is smooth and shiny. Do not over-process or the oils will begin to separate. (If this happens, just wipe the excess oil off the bars with paper towels. They will be slightly more fragile but still delicious.)

Pour the mixture in the prepared pan and press it down to create an even surface. Cover the pan and place it in the refrigerator for several hours, or overnight.

To make the chocolate ganache, whisk the coconut oil, cocoa powder, vanilla, honey and salt together until it is smooth and fluffy. The ganache can be spread on the brownies right after they are made or after they have chilled.

For the best results, store the brownies in the refrigerator for up to 2 weeks.