The finished recipe. Halloumi and Portobello Sourdough ToastieIngredients 1 to 6. 2 slices, about 100 g Sourdough. 60 g Halloumi. 1 large, about 80 g Portobello mushrooms. 30 g Spinach. 1 tsp (7 g) Balsamic glaze (The glaze is 40% sugar, so it is one teaspoon and weighed.). A few sprigs, leaves picked Fresh thymeIngredients 7 to 8. 3 sprays Olive oil spray (Counted at a quarter of a gram per spray, which is what the nozzle on most bottles delivers. Four sprays is 9 kcal.). To taste Black pepperStep 1. Slice the mushroom thickly and fry it in a sprayed pan over a high heat with the thyme for three minutes a side, until it has darkened and stopped leaking. Push it aside and fry the halloumi slices for two minutes a side.Step 2. Wilt the spinach in the pan for thirty seconds and press out the water.Step 3. Layer the mushroom, halloumi, spinach and glaze between the sourdough slices with pepper. Wipe the pan, return the sandwich to a medium-low heat with a weight on top, and toast for three minutes a side until crisp.