Preheat the oven to 300 degrees F. Bring about 3 cups of water to a boil. This is for the water bath. In a small saucepan over low heat, combine cream and milk. Cook until warmed throughout, but do not bring to a boil, about 5 minutes.
Combine sugar and lemon zest in a large bowl. Pinch together for about 1-2 minutes, until the sugar becomes fragrant (this releases the lemon oils for better flavor). Then add the egg yolks and lemon extract. Whisk together for about 2-3 minutes, until combined with the sugar and pale and fluffy.
Begin to pour the warmed heavy cream into the egg mixture, about a 1/2 cup at a time, whisking constantly so as to not to cook the eggs. Once all of the cream is added, add in the vanilla bean paste and a pinch of salt. Whisk together.
Place ramekins onto a baking sheet. Add about a 1/2 cup of the lemon custard mixture into each ramekin. Pour the hot water into the baking sheet and place into the preheat oven. Bake on the middle oven rack for 32-38 minutes, until the custard is set on the edges and slightly jiggly in the center (like jello).
Remove from the oven and place onto a wire rack. Allow the custard to come to room temperature, about 30 minutes, then place into the refrigerator to set for 4-6 hours.
Before serving, add a teaspoon of sugar on top of the custard in an even layer. Use a kitchen torch to caramelize the sugar and set aside to cool for 1-2 minutes. Then add an additional teaspoon of sugar on top, in an even layer, and caramelize again. Serve with fresh berries and a lemon peel, for garnish.
Notes
Torching Technique – Hold the torch at a 45° angle and keep it moving in a circular motion to evenly melt and caramelize the sugar without burning it in spots.When grating the lemons, avoid grating down to the pith. This can make your custard bitter.Temper the Egg Yolks – Whisk the egg yolks with sugar until pale and slightly thickened. Slowly stream in warm cream while whisking constantly to prevent scrambling.Cool Gradually – Let the custards cool in the water bath for about 30 minutes before transferring them to the fridge. This prevents sudden temperature changes that could cause cracking. Same theory as cheesecake.