To make the cheese sauce, bring a large pot of salted water to boil over high heat. Cut the potatoes and carrot into large chunks. Add to the boiling water and boil for about 15 minutes, until tender. Drain, then return to the pot.
Combine the potatoes, carrot, nutritional yeast, cashews, garlic, jalapeño, and lemon juice in a food processor. Purée until smooth