Traditional baked melktert (milk tart)

Name: Traditional baked melktert (milk tart)
Prep time: 20 min
Cook time: 1 h 30 min
Total time: 1 h 30 min
Yield: 8 slices
Ingredients: 20 g unsalted butter; 160 g plain flour; ½ tsp baking powder; 2 tsp caster sugar; 1 egg; 40 g chilled water; 2 pinches sea salt; 3 eggs; 2 cinnamon quills; 800 g full cream milk; 60 g unsalted butter; 1 tbsp natural vanilla extract; 40 g plain flour; 40 g cornflour; 120 g white sugar; 2 pinches sea salt; cinnamon sugar