Grilled Eggplant with Chick Pea Purée and Harissa

This recipe sounds odd, but it's really quite good. One time, lacking the potato, I used rice and corn instead. It's meant to be a side, I guess, but I usually serve it as a vegetarian main with a salad.

• Getting 12 slices out of a 10-oz eggplant is a big iffy. A bigger one or two smaller might be needed.
• 2/3 cup oil for brushing is way too much. I used 1/2 cup tonight and will go back to 1/3 cup next time. (Some of the leftover oil made a pretty good vinaigrette, and the rest will not go to waste.)
• 2 tbl butter is enough, but maybe a bit extra butter.
• The ingredient list has 3 garlic cloves; the instructions mention 4. It's up to you.
• If your harissa is salty, be careful in salting the mashed potato/chickpea part.