To make spiced pecans; preheat oven to 160°C. Combine butter, sugar, cinnamon, salt and chilli powder in a bowl. Add pecans and stir until combined. Spread nuts on an oven tray and roast for 15-20 minutes until beginning to colour. Cool. These can be made 2 days in advance.
To make biscuit base; put biscuits in a food processor and process to form crumbs. Add butter and cinnamon and process until combined. Tip mixture into the base of a 28cm round fluted quiche tin with removable base. Use the base of a straight sided glass to spread mixture over base and up the sides. Refrigerate.
To make filling; preheat oven to 160°C. Put cream in a saucepan and bring to a simmer. Put dark and Mexican chocolate in a heatproof bowl with butter. Pour in hot cream and stir until melted and smooth.
Whisk in eggs, chilli powder and cinnamon until combined. Put tart shell onto a large oven tray. Pour chocolate mixture into tart shell. Bake for 25-30 minutes or until tart is set but still has a wobbly centre. Cool.
To make icing; put cream in a saucepan and bring to a simmer. Place chocolate in a heatproof bowl. Pour in hot cream and stir until melted and smooth. Spread icing evenly over top of tart. Set in fridge for 2 hours. Arrange some of the pecans in the icing. Set in fridge again for 2 hours or until ready to serve. Serve with remaining pecans and whipped cream if desired.
Tip: This tart can be made up to 2 days in advance.