Place strawberries, 1/4 cup sugar, and lemon juice in a bowl, toss and let rest for 20–30 minutes so they release their juices. Mash lightly with a fork or pulse briefly in a food processor.

In a medium saucepan, combine the milk, heavy cream, and the scraped vanilla bean plus pod. Warm the mixture over medium heat until tiny bubbles form (do not boil). Meanwhile, whisk the egg yolks with the remaining 1/2 cup sugar and a pinch of salt until smooth and slightly paler.

Slowly pour about 1/2 cup of the hot milk mixture into the yolks while whisking continuously. Gradually add another 1/2 cup, then pour the tempered yolk mixture back into the saucepan with the remaining milk mixture.

Return saucepan to low heat and stir constantly until the mixture thickens slightly and coats the back of a spoon (170–175°F if using a thermometer). Remove from heat, take out the vanilla pod, and strain the custard through a fine-mesh sieve into a clean bowl.

Stir in the strawberry mixture (reserving a few chunks for swirls if desired) or add jam. Cover the bowl with plastic wrap and refrigerate until completely chilled, at least 4 hours or overnight.

Pour the cold custard into your ice cream maker and churn according to manufacturer’s directions until it reaches a soft-serve consistency. Add reserved strawberry pieces or mix-ins during the last few minutes.

Transfer to an airtight container and press a sheet of parchment onto the surface to prevent ice crystals. Freeze at least 4 hours to firm up.

Let sit at room temperature for 5–10 minutes before scooping. Top with fresh berries, a drizzle of strawberry syrup, or crunchy cookie pieces.