In a medium bowl, beat eggs with a fork, just until last traces of white are mixed in. Season with salt and pepper, and if you want to try herbs, you can use finely minced fresh parsley, chives, tarragon or chervil. Don't use dry herbs, unless you're a little insane.
In a medium nonstick skillet, melt butter, swirling over med-low heat (about 4 on our stove), until fully melted and foamy but not browned. Add eggs and stir rapidly with silicone whisk or plastic fork, tines up. Make sure to stir around edges and bottom to break curds. Stop stirring as soon as eggs are very softly scrambled and creamy, but still loose enough to come together into a single mass, 1 to 2 minutes.
Using fork, gently spread egg in an even layer around skillet and scrape down any wispy bits around the edges. The top surface should be loose and creamy, but if it looks too liquid and raw, let it sit for another few seconds. If it still flows, you can swirl skillet to send loose egg to the edges, where it will set more quickly. At this stage, you can add grated cheese on top if desired, then proceed with the next step.
Remove from heat. Tilt skillet up by its handle, and, using a fork and gravity, gently roll omelette onto itself. If it gets stuck, add a little butter to the pan and push it under the leading edge of the roll. When you reach the bottom third, push the omelette to edge of skillet til the unflipped edge of egg begins to go up the side; pull the far edge over the rolled omelette to complete the roll.
Hold skillet right over plate and turn omelette out onto it. It should be almond- or cigar-shaped, with the seam on bottom. At this point you can add in any bulkier add ins by cutting a fine slit lengthwise with a sharp knife and heaping them on top. You can get creative here with something like shrimp salad, hot sauteed mushrooms with thyme, or even something like braised short ribs in a red wine sauce.
