Sweat diced onions in butter.
Add corn kernels and cook until soft (About 15 minutes).
Add corn stock and simmer on low heat for about 20 minutes, leaving some liquid.
Season with salt to taste. Fold in epazote.
Serve warm in large bowl. Top with a light layer of Lime Mayonnaise, crumbled Queso Fresco and a gentle shake of Chile Piquin.
* For corn stock: Gently sweat onions and garlic in olive oil until very soft. Add corn cobs and water and cook until stock is very fragrant and flavorful, about one hour. Strain to remove cobs and onion and season to taste with salt.
* For the Lime Mayonnaise: Combine mayonnaise and lime juice in a small bowl and mix well. Season to taste with salt.