Begin by preparing the radicchio and grapefruit. Tear away the first few exterior darker leaves of the radicchio. Slice radicchio in half through the core. Cut out the core on each side then very thinly julienne the radicchio. Set aside.
Next, prepare the grapefruit. Slice off the top and bottom of the grapefruit.
Stand the grapefruit upright on the cutting board. Starting at the top of the grapefruit, guide your knife down to the base, curving the knife with the shape of the fruit. Continue all the way around the fruit until all of the rind and pith is removed. Use a paring knife to slice along the inside of the membranes, slide out your supremed grapefruit wedges and set aside.
Next, prepare the vinaigrette. Add all ingredients to a small mason jar and shake vigorously.
Finally, halve the avocado and remove the core. Carefully remove the flesh from the skin and set flesh face down on the cutting board then cut into lengthwise slices.
To assemble the salad, add the radicchio to the bottom of the platter in a circle. Next, in a circular pattern, alternate the grapefruit and avocado slices. Drizzle vinaigrette with a spoon all atop, saving some to finish.
Garnish with flaky salt, pistachios and mint leaves. Drizzle with more vinaigrette to finish and enjoy!