Prep first, then heat the pan. Crack the eggs into a bowl. Add the cream or yogurt, a pinch of salt, and a few twists of pepper. Whisk just until the yolks and whites are combined. You don’t need a froth, just a blended mixture. Set aside.
Cook the mushrooms. Set a nonstick or well seasoned skillet over medium heat. Add the butter or olive oil. When it’s hot and shimmery, add the sliced mushrooms in a single layer. Let them sizzle. Don’t move them for a minute or two, so they get golden edges.
Season and finish the mushrooms. Sprinkle with a pinch of salt and pepper. Stir and cook until the moisture in the pan evaporates and the mushrooms are browned, about 4 to 5 minutes total. If using garlic, add it in the last 30 seconds so it smells toasty but not burnt. Slide the mushrooms to one side of the pan or transfer to a small plate.
Lower the heat for the eggs. Drop the heat to low. If the pan looks dry, add a tiny dab of butter or a drizzle of oil. Pour in the egg mixture.
Soft scramble with patience. Using a silicone spatula or a wooden spoon, stir slowly, scraping the bottom and folding the curds as they form. Keep the heat gentle. The eggs should move slowly, like custard. If they race to the finish, the heat is too high.
Bring it together. When the eggs look mostly set but still glossy and slightly runny, fold in the mushrooms. Turn off the heat. The residual warmth will finish the eggs to a creamy, spoonable texture. Taste and adjust seasoning.
Dress the avocado. In a small bowl, toss the avocado slices with lemon juice, a pinch of salt, and pepper. This keeps them bright and adds a fresh top note.
Plate and serve. Spoon the creamy eggs and mushrooms onto warm plates. Tuck the avocado alongside or on top. Sprinkle with chives or parsley. Add red pepper flakes if you like a little sparkle of heat. Eat right away. Eggs wait for no one.