Macerate the strawberries. Use 1 pound of the strawberries for this step (save the remaining 1/2 pound for the cooked swirl). Chop the 1 pound into small pieces. Add to a bowl with 1/2 cup sugar, the lemon juice, and a pinch of salt. Stir and let sit 20 minutes. You are looking for a juicy, glossy bowl of berries.
Make a quick strawberry swirl. Chop the remaining 1/2 pound strawberries. Add to a saucepan with the remaining 1/4 cup sugar and 2 tablespoons of water. Cook over medium heat 8 to 10 minutes, stirring, until the berries break down and the mixture looks like a loose jam.
Blend if you want it smooth, or leave it chunky. Transfer to a bowl and chill until cold. Really cold. Warm swirl melts your churned base and can turn into an icy situation later.
Start the custard base. In a medium saucepan, warm the 1 cup whole milk and 1 1/2 cups heavy cream over medium heat until steaming and just beginning to bubble at the edges. Do not boil.
Note on sweetness: This recipe intentionally puts all 3/4 cup sugar into the strawberries (maceration plus swirl). Between that fruit syrup and the dairy, it lands in a classic, not-too-sweet zone. If you like your ice cream on the sweeter side, you can whisk 2 to 3 tablespoons sugar into the milk and cream while it warms. That also helps with softer scoops.
Whisk yolks and temper. In a bowl, whisk the egg yolks with a pinch of salt. Slowly pour in about 1 cup of the hot dairy while whisking constantly (this gently warms the yolks). Pour the mixture back into the saucepan.
Cook until it coats a spoon. Cook over medium-low heat, stirring constantly with a spatula, 4 to 7 minutes, until the custard thickens slightly and coats the back of a spoon. If you run a finger through it, the line should hold. Do not let it boil.
If you want a little extra certainty, the custard is usually ready around 170 to 175°F (77 to 80°C). Try not to push it past about 180°F (82°C) or it can scramble.
Strain through a fine-mesh strainer into a clean bowl. Stir in the vanilla and the optional corn syrup or vodka if using. (A small splash is great. Too much alcohol can keep things slushy, but 1 tablespoon in a quart batch is a safe, helpful range.)
Chill the base. Press plastic wrap directly on the surface (this prevents a skin), then refrigerate until very cold, at least 4 hours (overnight is even better). Cold base equals smoother ice cream.
Finish the strawberry mix-in. Drain the macerated strawberries in a strainer set over a bowl. Save the syrupy juice. If the berries seem very wet, you can gently blot them with a paper towel. Keep the pieces small so you do not end up with frozen berry rocks.
Stir some of the reserved strawberry syrup into the cold custard for extra berry pop. Start with 2 tablespoons, then taste. You can go up to about 1/4 cup max, but do not flood it or you invite iciness back to the party.
Churn. Churn the cold base in your ice cream maker according to the manufacturer instructions, usually 20 to 30 minutes, until it looks like soft serve.
Fold in berries, then ripple. Fold the drained macerated strawberry pieces into the churned ice cream. Spoon one-third of the ice cream into your freezer container, add a few spoonfuls of the chilled strawberry swirl, then repeat. Use a knife tip to gently ripple, just a couple of passes so you keep distinct swirls.
Freeze to set. Cover and freeze 3 to 4 hours until scoopable.
