Méthode Champenoise is not actually a varietal (meaning a type of grape), but rather it refers to a specific method of making sparkling wine. This method is named after the Champagne region of France and it is the process by which true Champagne is produced.
In the Méthode Champenoise, the wine undergoes a primary fermentation in barrels, after which the wine is bottled with a mixture of sugar and yeast. The bottles are then sealed and stored horizontally for secondary fermentation. This fermentation produces carbon dioxide in the bottle, which creates the bubbles characteristic of sparkling wine.
After the secondary fermentation, the yeast cells die and sediment forms in the bottle. The bottles are gradually tilted and rotated to collect this sediment (or "lees") in the neck of the bottle, in a process called "riddling."
Finally, the sediment is removed in a process called "disgorgement." The cap is quickly removed, and the pressure from the carbon dioxide forces the sediment out. This is then replaced with a mixture of wine and sugar, called "dosage," which determines the sweetness of the final product. Then, the bottle is corked and sealed.
The result is a fizzy, often dry and complex wine that can range from light to full-bodied. Notable grape varietals used in this method include Chardonnay, Pinot Noir, and Pinot Meunier.
