Walnut Ice-cream

Ingredients

Equipment Needed

• •Small paring knife
• •Mortar and pestle or mini food processor
• •2-quart heavy saucepan
• •Instant-read thermometer
• •Fine-mesh sieve
• •Immersion blender
• •Ice cream maker
• •1-quart freezer container

Instructions

1. 1

   Peel the walnuts

   Drop the walnut kernels into a small pan of boiling water and blanch them for 60 to 90 seconds. Drain a few at a time, keeping the rest warm, then rub away the loosened brown pellicle with a clean towel and lift stubborn patches with the tip of a small paring knife. Return any obstinate kernel to the hot water rather than scraping away its flesh. Spread the peeled walnuts on a towel and pat them dry. Do not toast them; the source calls for their pale, milky flavor, not roasted depth.

   Peel while the walnuts are warm. Once cold, the skins tighten again and turn a patient job into an argument.
2. 2

   Pound to a paste

   Put the peeled walnuts in a mortar or mini food processor. Add the cool water one tablespoon at a time and pound or process, scraping frequently, until the nuts become a very fine ivory paste with no pieces larger than coarse sand. Stop before the walnut oil forms a separate slick. If it begins to separate, add one spoonful of the measured milk and work briefly until the paste comes together again. Ça se rattrape.

3. 3

   Infuse the milk

   Bring the whole milk to a full boil in a heavy saucepan, stirring across the bottom so it cannot scorch. The moment it rises, remove it from the heat and whisk in the walnut paste. Cover and leave it undisturbed for exactly 20 minutes. This infusion is not brigade scaffolding and cannot be hurried; it draws the walnut's perfume and oil into the milk without cooking the nuts harshly.

4. 4

   Cook the crème anglaise

   Whisk the egg yolks, sugar, and salt in a heatproof bowl until smooth and slightly pale. Reheat the infused milk until it trembles at the edge, then pour it into the yolks a little at a time while whisking. Return everything to the saucepan and cook over low heat, stirring constantly across the floor and into the corners, until the crème anglaise reaches 79 to 82°C and coats the back of a spoon. The walnut paste gives the mixture body before the yolks are fully cooked, so trust the thermometer as well as your eye. Never let it boil. At the first sign of graininess, take it off the heat, whisk in ¼ cup of the measured cold cream, blend briefly with an immersion blender, and strain at once. Ça se rattrape before the yolks become firm curds.

5. 5

   Strain and chill

   Pass the custard through a fine-mesh sieve into a clean bowl, pressing the walnut pulp gently but thoroughly with the back of a ladle. Discard the dry, fibrous residue. Whisk in all the cold cream, or the remainder if some was used to rescue the custard. Set the bowl over ice and stir until completely cool, then cover and refrigerate for at least 4 hours. A thoroughly cold base freezes quickly and forms smaller ice crystals; a merely cool one churns heavy and coarse.

6. 6

   Churn until dense

   Churn the cold base in an ice cream maker according to its instructions, usually 20 to 25 minutes, until it holds soft folds and has the density of thick crème fraîche. Do not wait for it to become hard in the machine. Overchurning warms the mixture and can leave butter grains on the tongue.

   Without a machine, pour the base into a shallow metal pan and freeze it, beating vigorously every 30 minutes while scraping the frozen edges into the center. Repeat until evenly frozen, about 3 hours. The texture will be denser, but the walnut flavor remains true.
7. 7

   Harden and serve

   Pack the churned glace aux noix into a shallow freezer container, press parchment directly against the surface, cover, and freeze for at least 3 hours. Let it stand at room temperature for 8 to 10 minutes before scooping. It should be pale ivory, finely textured, and supple enough to curl from the scoop rather than crumble. Serve it generously and without decoration. À table!

Chef Tips

• •Buy the freshest walnuts you can and taste one before beginning. A rancid walnut smells of old oil and stays rancid under sugar and cream; technique can refine a modest nut, but it cannot restore a spoiled one.
• •The brown pellicle is not a harmless cosmetic layer. It carries the tannic bitterness that spoils this delicate infusion, so blanch, peel, and rewarm stubborn kernels until every patch is gone.
• •Do not toast the walnuts. Toasted walnut ice cream can be pleasant, but it is another formula. This one depends on the clean, almost milky perfume of peeled raw kernels.
• •Chill the custard until it is cold all the way through before churning. If time allows, leave it overnight; the walnut flavor becomes rounder and the texture freezes more finely.
• •Keep the finished ice cream tightly covered with parchment against its surface. It is best within one week, before freezer odors and oxidation flatten the walnut's delicate aroma.

Advance Preparation

• •The walnuts can be blanched and peeled one day ahead. Dry them well, seal them airtight, and refrigerate until you are ready to pound them.
• •The strained custard base can be refrigerated for up to 24 hours before churning. This rest deepens the infusion and ensures the base is thoroughly cold.
• •Churn and harden the glace aux noix the day before serving. Let it soften for 8 to 10 minutes before scooping.

Frequently Asked Questions

Nutrition Information

1 serving (about 135g)