Preheat oven to 200C. Turn on ice cream machine to chill according to manufacturers instructions.
For the Profiteroles, place butter and 110g of water into a small saucepan over medium heat and stir until melted. Once butter has melted, add flour and whisk vigorously until the mixture comes away from the sides of the pan and forms a soft dough, about 2-3 minutes.
Transfer the dough to a stand mixer fitted with a whisk attachment and whisk on high until the dough has cooled slightly. With the mixer still running, add eggs, one at a time, ensuring fully incorporated before each addition. Continue to whisk until the dough is smooth and glossy. Transfer dough to a piping bag.
Line a baking tray with baking paper. Snip the piping bag and pipe 5cm diameter rounds of the dough onto the lined tray about 5cm apart. Place into the oven and bake until golden and puffy and cooked through, about 30 minutes. Remove from oven and use a skewer to pierce a small hole in the bottom of each profiterole. Reduce oven temperature to 170C.
Place profiteroles back into the oven for 10 minutes to dry out. Remove from oven and set aside to cool completely.
For the Lemon and Fennel Ice Cream, place fennel seeds into a mortar and pestle and crush coarsely. Place milk, cream and crushed fennel seeds into a small saucepan over low heat and bring to just below boiling point. Remove from heat and set aside to infuse for 5 minutes.
Meanwhile, whisk lemon juice, egg yolks and caster sugar in a medium bowl until pale. Slowly pour mixture into the hot milk and cream mixture, whisking continuously until combined. Strain through a fine sieve into a clean saucepan and place back over low heat, stirring continuously until mixture thickens and coats the back of a spoon, about 5 minutes. Remove from heat and cool over an ice bath. Once cool, transfer to the ice cream machine and churn until set. Once set, transfer to freezer until needed.
For the Lemon Curd, place yolk, sugar, lemon zest and juice in a small saucepan over low heat and whisk until sugar has dissolved. Gradually whisk in the butter, ensuring butter has melted before each addition. Continue to whisk until curd has slightly thickened, about 4-5 minutes. Transfer to a pouring jug and set aside until needed.
For the Candied Lemon Zest and Lemon Glaze, combine lemon juice and caster sugar in a small saucepan over low heat and stir until sugar has dissolved. Remove from heat and set aside.
Meanwhile, place two small saucepans of water onto high heat and bring to the boil. Prepare a bowl of iced water. Once saucepan of water is boiling, add lemon zest to one of the saucepans and blanch for 30 seconds then remove and plunge into iced water. Repeat this process with the second saucepan of clean boiling water then plunge zest into iced water again then strain.
Add blanched lemon zest to the saucepan of lemon syrup. Place over low heat and simmer until the syrup has thickened slightly and zest has become translucent, about 5 minutes. Remove zest from syrup and lay out on a sheet of baking paper. Set zest and syrup aside until required.
Increase oven temperature to 190C.
For the Lemon Zest Tuille Crumb, line a baking tray with baking paper. Place egg white into a medium bowl and whisk to soft peaks. Whisk in caster sugar then fold in flour, butter, lemon zest and mix until fully incorporated. Use an offset spatula to spread the tuille mixture thinly onto the lined tray then bake in the oven until golden, about 5-7 minutes. Remove from oven and set aside to cool. Once cool, transfer to a food processor and process to a crumb. Set aside.
To plate, use a pastry brush to brush some of the Lemon Glaze across the plate. Cut Profiteroles in half. Lay 4 of the Profiterole base halves along the smear of glaze on the plate. Dip the top half of each Profiterole into the Lemon Glaze and place a strip of Candied Lemon Zest on top. Place a scoop of the Lemon and Fennel Ice Cream on top of each Profiterole base then place the glazed top halves on top. Scatter some Lemon Zest Tuille Crumb between the profiteroles. Serve Lemon Curd on the side.