Prepare the rim: Mix 1 part Tajín with 1 part kosher salt on a small plate. Run a lime wedge around the rim of your glass, then dip and twist into the mixture. Set aside to dry.
Choose your style: Decide if you want it on the rocks or frozen.
For on the rocks, you’ll shake with ice. For frozen, you’ll blend with ice.
Muddle the heat (on the rocks): In a shaker, add 1–3 jalapeño slices. Gently muddle for 5–10 seconds.
Don’t overdo it or the drink can turn bitter.
Add the base (on the rocks): Add 2 oz tequila, 1 oz triple sec, 1 oz fresh lime juice, 1/2–1 oz agave, and 3–4 oz mango (puree or well-mashed fresh). Fill with ice and shake hard for 12–15 seconds.
Strain and serve (on the rocks): Fill your rimmed glass with fresh ice. Double strain the margarita to catch seeds and pulp.
Garnish with a lime wheel and a jalapeño slice.
For a frozen version: In a blender, combine 2 oz tequila, 1 oz triple sec, 1 oz lime juice, 1/2–1 oz agave, 1/2 cup frozen mango, 1–2 jalapeño slices, and 1 to 1 1/2 cups ice. Blend until smooth and pour into the rimmed glass.
Taste and adjust: If it’s too tart, add a touch more agave. If it’s too sweet, add a squeeze of lime.
If you want more heat, float a thin jalapeño slice on top.
Optional garnish: Mango slice, chili-lime dusting on top, or a sprig of cilantro for aroma.