Mix graham crumbs, sugar, melted butter, salt until resembles wet sand
Spoon 2-3 tbsp into each cup, press firmly
Refrigerate while making filling, at least 15 minutes
Whisk condensed milk, lime juice, egg yolks, lime zest, salt for 2-3 minutes until smooth and thickened
Remove cups from fridge
Divide filling evenly among cups over crust
Leave ½ inch at top for cream
Tap cups gently to remove air bubbles, smooth tops
Refrigerate at least 2 hours or overnight until set
Just before serving, beat cold heavy cream with mixer on medium-high
Once thickening, add powdered sugar and vanilla
Beat to stiff peaks, don't overbeat
Spoon or pipe whipped cream onto chilled cups
Garnish with lime zest, lime slice, graham crumbs, mint
Serve immediately or refrigerate up to 2 hours