The omelet also provides around 1.5 g of "good" polyunsaturated fat, but the rest of the fat is saturated. Each gram of fat provides 9 calories. Add onion and garlic; cook, stirring often, until softened and tender, about 5 minutes. About one-half the fat is monounsaturated. A one-egg spinach and mushroom omelet has nearly 8 g total fat. Add mushrooms; cook, stirring occasionally, until browned and tender, about 8 minutes. Heat oil in a large nonstick skillet over medium-high heat; swirl to coat the pan. Add the Add spinach; cook, tossing constantly, until wilted, 1 to 2 minutes. Remove from heat. Melt the butter in an 18cm (7in) diameter non-stick omelette pan and fry the mushrooms with the garlic until they're a deep golden brown and beginning to go crisp around the edges. This omelet provides 71 calories from fat, which is 65 percent of the total calories for the dish. Melt a knob of butter in a frying pan placed over a medium heat.