Prepare the glass: Run a lime wedge around the rim of your glass. Dip in salt or tajin if you're feeling it. Set aside.
Muddle the jalapeño: Put jalapeño slices in the bottom of a cocktail shaker. Gently muddle to release the oils and spice.
Add remaining ingredients: Pour in the tequila, triple sec, mango puree, lime juice, and agave nectar.
Shake well: Add ice to the shaker, secure the lid, and shake hard for 15-20 seconds until it's nice and cold.
Strain and serve: Double-strain through a fine mesh strainer into your prepared glass filled with fresh ice.
Garnish: Add a lime wheel, mango slice, and jalapeño ring to the rim. Looks good, right?