Add the butter and olive oil to a large non-stick skillet or pan.: Listen for the immediate sizzle as the butter hits the warm surface, and watch the fat shimmer with tiny ripples. The combination of butter and olive oil raises the smoke threshold and creates a flavor base that coats the spinach . You want the pan hot enough that the oils move freely, but not smoking, so you avoid burnt butter notes. A common mistake is overheating the fat, which can scorch the butter and give an acrid taste. If you see dark specks in the fat, lower the heat and wipe the pan, then start again. This initial stage sets the aroma and texture foundation for the whole dish.
Once hot, add the garlic, then the spinach, salt, and pepper, and saute for 2-3 minutes, or until wilted.: Right after the oil is shimmering, add the minced garlic and pay attention to the sound it makes, a soft popping that mellows as it releases fragrance. Immediately add the spinach in handfuls so the heat drops slightly and the leaves begin to collapse. You should hear a gentle hiss as moisture escapes, and the leaves will quickly turn a deeper, glossy green. I like to toss or stir constantly to ensure even wilting and to keep the garlic from sticking to the pan. The salt helps pull liquid from the leaves, concentrating flavor, while the pepper adds a background warmth. Watch for signs of overcooking such as a slimy texture or a dull, dark color, which indicate you left the spinach in the heat too long. If that happens, remove it promptly to a bowl to stop the cooking process.
Remove the spinach from the pan and serve with lemon slices.: As the leaves reach a tender wilt, they will become glossy and reduce drastically in volume, signaling it is time to take them off the heat. Use a spatula or tongs to lift the spinach so it sheds excess oil back into the pan, keeping the texture light rather than drenched. Serving immediately is important because residual heat will keep cooking the greens. A common issue is holding the spinach in the pan too long while plating other components, which makes the leaves soggy. Transfer to a warm plate and offer acidity, such as lemon, at the table to brighten the flavors just before eating. The final aroma should be buttery with a clean garlic note and the color should remain vibrant.