Step 1: Make the Lemon Curd.

In a heat-proof bowl (or the top of a double boiler), beat the egg yolks for 1 minute.

Add the maple syrup or sugar. Beat for another minute.

Add the lemon juice and zest. Mix well.

Place the bowl over a pan of simmering water (make sure the bottom of the bowl isn’t actually touching the water).

Cook, stirring nearly constantly, until the curd thickens, about 10–20 minutes. It should coat the back of a spoon.

Stir in the butter, 1 piece at a time, waiting until each piece melts before adding another one.

Remove from the heat.

Strain the curd through a fine-mesh sieve into a storage jar.

Cool until just warm.

Cover and refrigerate until set, at least 2 hours.

Step 2: Make the Ice Cream Base.

In a large mixing bowl, beat the heavy cream, sugar, and vanilla extract with a hand mixer until the cream is thickened but not quite enough for dolloping. You want it to be a little liquid and not able to hold peaks.

With the mixer on low speed, slowly pour in the milk. Mix until well combined.

Step 3: Churn the Ice Cream.

Churn the mixture according to your ice cream maker’s instructions.

Don’t over-churn. Because you’ve already beaten the cream, it’s easier to churn your ice cream too long and give it a buttery texture. Stop and check the ice cream at least 5–10 minutes before you normally would.

Step 4: Ripple in the Lemon Curd.

Once the ice cream is churned, scoop it into a freezer-safe container.

Dollop half of the lemon curd over the top.

Fold it into the ice cream with a spatula.

Dollop the remaining lemon curd over the top.

Fold it in again.

Step 5: Freeze the Ice Cream.

Freeze for several hours, or until firm. Depending on how cold your freezer is, this could take as little as an hour, or up to 4 hours.