Preheat oven to 350 and line a 9x9 pan with parchment.
Shortbread: Combine flour, sugar, salt and butter in large bowl, stand mixer or food processor. Combine thoroughly. Press dough into parchment- lined 9X9 baking dish then place in fridge to chill.
Mango Layer: Puree mango in food processor until smooth. In a separate bowl, whisk granulated sugar with flour. Then add in eggs , lime juice, mango puree, and vanilla extract. Pour over shortbread layer. Bake for 23-25 minutes. Mango layer should be set/ firm to touch. Let cool.
Chocolate Drizzle: Microwave chocolate for 2 minutes, stopping every 15-20 seconds to mix with spatula. When chocolate is almost entirely melted, add butter and whisk together. The heat from the chocolate will slowly melt butter and mixture will become glossy. Drizzle to your heart's content!