Run a lime wedge around the rim of your glass and coat in flaky salt. In a cocktail shaker or glass jar, add the blackberries, jalapeños, lime juice, and honey. Muddle all of the ingredients together, squashing everything to release the juices from the fruit. Add the tequila and orange liquor. Fill with ice and shake until combined. Strain into a glass, then pour back into your cocktail shaker. Add ice and the egg white, if using. Shake vigorously until fizzy on top, about 1 minute. Strain into a glass. Drink and enjoy!