Crust
Step 1
Spray an 8×8″ metal baking pan with nonstick vegetable oil spray and line with 2 sheets of parchment paper, leaving overhang on all 4 sides. Pulse 20 Maria cookies (4–5 oz.) in a food processor until fine crumbs form, about 30 seconds. Add ½ cup (1 stick) unsalted butter, melted, 1 Tbsp. plus 1 tsp. light brown sugar, and 2 tsp. Tajín Clásico or other chile-lime seasoning and pulse just until cookie crumbs are moistened, 10–15 pulses. (Alternatively, you can pound cookies in a resealable plastic bag with a rolling pin, then add butter, brown sugar, and Tajín and massage to combine.)
Step 2
Transfer mixture to prepared pan and press firmly and evenly across bottom with a measuring cup. Freeze crust, uncovered, while you make the filling.
Filling and Assembly
Step 3
Whisk together one 4-oz. bag frozen mango pulp, thawed, or 1¾ cups mango nectar, juice of 1 lime, 1¼ cups (250 g) granulated sugar, ⅓ cup cornstarch, and ¼ tsp. Diamond Crystal or Morton kosher salt in a medium saucepan until no lumps remain. Set over medium heat and cook, whisking constantly, until mixture comes to a gentle simmer (it should be slowly bubbling) and is thick enough to coat a spoon, 6–8 minutes. Immediately remove from heat.
Step 4
Whisk 5 large egg yolks and 2 large eggs in a medium heatproof bowl until smooth. Pour about half of hot mango mixture into egg mixture, whisking constantly; continue to whisk until combined. Transfer egg mixture to saucepan with remaining mango mixture and cook over medium heat, whisking constantly, until curd is thick enough to thickly coat a spoon, about 5 minutes. Add 6 Tbsp. unsalted butter, cut into small pieces, and cook, whisking constantly, until butter is melted and incorporated into curd, 2–3 minutes. Scrape curd into a large bowl and let cool 10 minutes. Stir 1 Tbsp. vodka, if using, into mango curd and let curd cool completely, 25–35 minutes.
Step 5
Vigorously whisk ⅓ cup heavy cream in a medium bowl until stiff peaks form, about 3 minutes. Fold whipped cream into cooled mango curd to combine. Pour mixture over chilled crust, smooth surface, and freeze until firm enough to support the mango but not so frozen that it is rock solid, at least 2 hours and up to 4 hours.
Step 6
Bring ½ cup chamoy and ¼ cup (packed; 50 g) light brown sugar to a boil in a small saucepan over medium heat. Cook, stirring often, until sugar is melted and mixture is thickened and syrupy, about 3 minutes. Let syrup cool.
Step 7
Evenly spoon chamoy syrup over filling. Scatter 1 large mango (such as Ataulfo or Champagne), peeled, cut into ½” pieces, over in a single layer, pressing into syrup slightly to adhere and sprinkle generously with Tajín Clásico or other chile-lime seasoning. Freeze until frozen (topping should feel solid and not give way when gently pressed), at least 6 hours.
Step 8
When ready to serve, using parchment overhang, lift bars out of pan and onto a cutting board. Cut into a 4×4 grid to make 16 squares.
Do Ahead: Bars can be made 1 month ahead. Cover tightly and keep frozen.