Note: If you're using pistachios, no need to toast the hazelnuts. Preheat oven to 375 degrees. Roast small handful of hazelnuts for 10-12 minutes (until golden brown). Transfer the hazelnuts to a clean kitchen towel and rub to remove the skins and then chop. Segment the grapefruit, toast the bread, and mash avocado. To assemble, smear the mashed avocado onto your piece of bread, top with a few slices of grapefruit, drizzle on olive oil, add pistachios or hazelnuts and top with a sprinkling of sea salt.