• Gather all of the ingredients and measure them out. Crack 45 g egg yolks into a small bowl and whisk well. Set aside.
  

Make the Pistachio Paste:

• Place 120 g shelled pistachios in a food processor and blend until finely minced. Add 4 g neutral oil and continue blending until it forms a relatively smooth paste. Set aside while you cook the custard base.
  
You can process for longer for a smoother result. You can also optionally strain out any chunky bits later, so the final texture is not as important here.

Make the Pistachio Ice Cream Base:

• Pour the 150 g cane sugar and 0.3 g guar gum (if using) into a 2-quart saucepan and whisk.
  
• Add the 60 g skim milk powder and whisk.
  
• Prepare an ice bath by filling a large bowl with cold water and several handfuls of ice cubes. Set aside.
  
• Pour 400 g whole milk into the pan with the sugar/SMP mixture, and whisk until the sugar/SMP have mostly dissolved.
  
• Add 400 g heavy cream and whisk again until the mixture feels smooth.
  
• Gently heat the pot over medium-low, whisking constantly, until it reaches 110°F on an instant-read thermometer. Once it reaches temperature, immediately remove it from the heat.
  
• Take a ladleful of the warm cream mixture, and stream it slowly into the egg yolks, whisking vigorously to prevent curdling. Once the mixture is smooth, pour the egg/cream mixture back into the saucepan, and whisk well until the liquid takes on a yellowish hue.
  
• Return the pan to medium-low heat, and continue warming, whisking constantly, until it reaches 165°F. Once at temperature, immediately remove it from the heat.
  
• Set a fine-mesh sieve over the smaller bowl you set aside for the ice bath. Strain the hot custard into the bowl.
  
• Place the bowl into the ice bath and whisk often for about 15 minutes, or until the custard reaches about 75°F.
  
• Add all of the pistachio paste and use an immersion blender to blend it into the ice cream base until everything has coalesced into a creamy custard. Add 4 g almond extract now, if using.
  
Taste and add a pinch of salt if needed. I used salted pistachios, so I did not add additional salt.
• Cover the custard with plastic wrap and refrigerate for at least 4 hours, or up to overnight.
  

Make the Rhubarb Jam:

• While the ice cream base chills, clean the immersion blender — you'll need it again. Chop the rhubarb and juice the lemon.
  
• Add 113 g fresh rhubarb, 113 g cane sugar, and 7 g fresh lemon juice to a medium saucepan set over medium-high heat, stirring until the sugar melts. Continue cooking, stirring frequently, until the mixture reaches 224°F (the rhubarb will break down, and the mixture will go from chunky to saucy as it climbs). Remove from heat and blend.
  
For a full visual walkthrough of the jam, see my rhubarb jam swirl post.
• Pour into a heatproof container and cool at room temperature for at least 1 hour, then refrigerate until completely cold before using.
  

Churn and Swirl the Ice Cream

• Once the custard has chilled, pre-chill your ice cream maker according to the instructions. Pour in the custard with the machine running.
  
• Allow the custard to churn according to the machine's instructions. This will take anywhere from 20-45 minutes, depending on the machine.
  
You'll know it's ready when the machine starts to slow down and struggle, and the ice cream has a soft-serve consistency. Ideal draw temperature is 18-21°F.
• Fill each container about ⅓ full with pistachio ice cream, then dollop 1-2 tablespoons of rhubarb jam on top. Use a chopstick or butter knife to gently swirl the jam into the ice cream. Repeat these steps until each pint is full.
  
• Press wax paper onto the surface of each pint to prevent ice crystals, and set in the freezer for at least 4 hours, or overnight, to fully set and age.