Flan Pâtissier (French Custard Tart)

Creme Patissiere:

1. Infuse milk: Place milk, vanilla seeds, used beans and 50g (1/4 cup) sugar in a large saucepan over medium high heat. Bring to just before boiling, stirring to dissolve the sugar. Remove from heat, place lid on and leave to steep for 10 minutes.
2. Yolk mixture: Meanwhile, place egg yolks, egg and remaining sugar in a large bowl and whisk to combine. Add cornflour and whisk until smooth.
3. Temper eggs: While whisking the eggs, slowly pour in about half the milk in a thin stream. Whisk until combined.
4. Thicken custard: Pour the egg-milk mixture back into the saucepan then whisk to combine. Place over medium low heat, stirring constantly so the base doesn't catch, until it starts to thicken (you will feel it). It should happen within 3 to 5 minutes. If it gets lumpy, remove off heat, whisk vigorously - will become smooth.
5. Stir 20 seconds after bubbles appear: When the custard is thickened and hot and you see the first big lazy bubbles appear on the base, whisk constantly on the stove for a further 20 seconds then remove from stove. (To check for bubbles, pause stirring for a few seconds)
6. Butter: Whisk butter in until fully incorporated.
7. Strain & cool: Immediately strain into a bowl through a fine mesh strainer. Discard vanilla bean. Cover with cling wrap touching the surface. Cool on counter (3 hrs+) then refrigerate 12 - 24 hours. (Note 5)

Crust:

1. Work with pastry as frozen as possible - it's easier. (Note 4)
2. Cut base and sides: Cut base out using the inside of the pan as a guide on one sheet of puff pastry. Cut three 25 x 5.5cm  (2.15 x 10″) wide strips on the other sheet of puff pastry. Place base and sides back in freezer. RESERVE offcuts (for emergency patching).
3. Line pan: Butter and line the sides of a 20cm/8" springform pan with a 5.5cm / 2.2" strip of baking paper. We are not using the pan base. (Note 6)
4. Line sides: Place cake pan on a square sheet of baking paper on a plate. (Note 6) Remove cut puff pastry from freezer. Working quickly, when sides have JUST thawed enough to bend, line sides of cake pan with puff pastry, overlapping by 1cm / 0.4", using water to seal - just press down for now (will seal properly later).
5. Base: Brush base of sides with water. Fit base into cake pan (see video at 2 min 50 sec for technique).
6. Seal pastry: Use the back of a teaspoon to press base into the corner. Then smear the now-thawing puff pastry to full seal.
7. Prick base: Prick base 30 times with fork. (I always forget!!)
8. Freeze: Cover with cling wrap, freeze 4 - 24 hours. (Note 4)

Bake:

1. Preheat oven to 220°C/430°F (200°C fan) for 30 minutes.
2. Line & fill with beads: Pick up crust using paper and place on tray (on the paper). Crumple 2 x 60cm / 2 feet long sheets of baking paper (Note 7) then fit into crust arranged in X. Fill with baking beads 1cm / 0.4" below rim (Note 8). Press to push paper into corners.
3. Blind bake 25 min + 5 min: Bake 25 minutes, then use overhang paper to remove beads carefully (if sides look like they will cave in, return to oven with beads for 5 min). Bake 5 minutes then cool 10 minutes. (Seal any visible cracks with puff pastry scraps)

Assemble Flan Pâtissier:

1. Turn oven down to 200°C/390°F (180°C fan).
2. Fill with custard: Remove Creme Patissiere from fridge. Whisk to loosen, scrape into crust - fill to 1cm/0.4" below rim. (Leftover custard Note 7) Smooth surface, brush custard surface with egg yolk (use it all).
3. Bake 65 minutes, rotating tray 180° at 45 minutes. It will puff up in the last 15 ninutes like a souffle. Remove from oven - it will still be very wobbly, have faith! It will set when cool!Golden surface - If the top is not golden like pictured, switch on broiler to caramelise surface. Watch carefully - takes minutes!
4. Cool on counter for 4 hours (in pan). Transfer to plate (still in pan), cover loosely with cling wrap, then refrigerate 12+ hours.
5. Serve: Remove from fridge 1 hour prior to serving to bring to room temperature. Cut into slices like cake! The pastry is crispy & flaky. The custard will cut neatly (it will not ooze) but when you bite into it, the custard is beautifully soft and creamy. Traditionally eaten as a hand held bakery treat in France but you can use a plate if you're feeling civilised!
6. Shelf life: Flan Pâtissier is at its best in the first 24 hours after it is put in the fridge after baking as this is when the pastry is still beautifully crisp. Beyond this the pastry starts to soften which no one has pointed out yet because everyone is besotted by the custard! But I notice. :)