Using a large knife, slice the kernels off the corn cobs and place in a large saucepan.

Break cobs in half and add to pot along with milk, cream and 1/2 cup sugar.

Bring mixture to a boil, stirring, then remove from heat.

Let stand to infuse for 1 hour, then discard corn cobs.

Using an immersion or regular blender, purée kernel mixture.

Return mixture to a simmer, then turn off heat.

In a small bowl, whisk egg yolks, 1/8 teaspoon salt and another 1/4 cup of sugar.

Add a cup of hot cream mixture to the yolks, stirring constantly so they don’t curdle.

Add yolk mixture to saucepan, stirring. Cook over medium-low heat, stirring constantly, until custard thickens enough to coat the spoon, about 10 minutes.

Pass custard through a fine sieve, pressing down hard on the solids. Discard solids.

Whisk in vanilla and sour cream until smooth.

Let custard cool in an ice bath, then cover and chill for at least 4 hours.

Freeze the custard in an ice cream maker (use the directions for your specific model). We have an attachment for our Kitchen Aid stand mixer, which works pretty well.

Once the custard is a soft-serve consistency, move it to an air-tight container and freeze for another couple of hours.