With the back of a chef’s knife, mash the garlic with a pinch of salt into a paste. Add the egg, garlic paste, and lemon juice to a blender and secure the lid.
Blend on medium speed while pouring the grapeseed oil into the blender in a slow, steady stream. Go slowly so as to not break the emulsion. Once the grapeseed oil is fully emulsified, drizzle in the extra-virgin olive oil with the blender running until incorporated. The aioli should be very thick and pale in color at this point.
Stir the almond butter into the aioli. To make the aioli a pourable sauce, thin it by stirring in 2 or 3 Tbsp of ice water. Taste and season with salt.
Store any leftover aioli in an airtight continuer in the refrigerator for up to 3 days.
Make the Almond Picada
In a small, dry frying pan, toast the almonds over medium heat until fragrant, about 3 minutes. Let cool and coarsely chop. In the same pan, toast the almond meal until fragrant, about 1 minute. Let cool.
In a mortar with a pestle, combine the almonds, garlic, lemon zest. Smash the ingredients into a coarse paste. Add the almond meal and parsley and continue to mash until incorporated. Stir in the extra-virgin olive and season with salt and pepper.
Roast the Squash
Preheat the oven to 425°F.
Season the acorn squash with kosher salt and freshly cracked black pepper. Put the squash cut-side down in a large roasting pan. Add the water to the pan, cover with aluminum foil, and roast for 20 minutes. Remove the foil, add 2 tbsp of butter to the pan, and continue roasting until golden brown, about 15 minutes.
Transfer the squash to a serving platter, drizzle some of the almond aioli over the squash, and then scatter the picada on top. Season with flaky salt. Serve warm.
Homemade aioli may sound intimidating, but it’s relatively straightforward — especially if you take some assistance from your blender.Aioli is an emulsion made from garlic, eggs, acid, and oil. The trick to a thick, creamy, and infinitely spreadable aioli is pacing. If you add the oil in one glug, it will separate forming a watery, curdled mess. Instead, slowly add the oil a little at a time — starting with just a few drops. Once the mixture starts to look creamy, add the remaining oil in a thin, steady stream until thick and pale.If you break your aioli, there is a fix: Put an egg yolk into a clean bowl and whisk in the broken aioli, drop by drop.