Peel and quarter 1 banana lengthwise and trim away the dark center seeds. Using a food processor, puree the quartered banana, ricotta, sugar and vanilla for 1 to 2 minutes.
Thinly slice the remaining bananas crosswise and spread them on 2 large plates (you want about 42 slices). Grate enough fresh nutmeg over the slices to lightly coat one side.
Reserve 3 tablespoons of the toasted almonds. Then, into each of 6 parfait glasses (about 1 cup capacity), place a banana slice nutmeg side up, a sprinkle of almonds and about an inch of the banana-ricotta puree. Layer with 3 more banana slices, a sprinkle of almonds and an inch of puree; repeat this layering once more to fill the glasses. Cover and refrigerate until ready to serve, at least 1 hour and up to 4 hours. Just before serving, sprinkle with the reserved almonds.