Thinly slice the Onion (1). Mince the Garlic (1 clove). Roughly chop the Mushroom (12 ounce) and Tomato (1). Halve the Red Creamer Potato (10 ounce), and chop the Italian Flat-Leaf Parsley (1 tablespoon).
In a saucepot, combine potatoes, fresh Fresh Rosemary (2 sprig), a pinch of Kosher Salt (to taste) and cover with water by one inch. Over high heat, bring to a boil, and remove rosemary. Turn heat down, and simmer until potatoes are tender.
While potatoes are cooking, heat a saute pan over medium-high heat, add the Olive Oil (1 tablespoon) and half of the Unsalted Butter (2 tablespoon). When the butter has melted, add the sliced onion and minced garlic and cook for 3-4 min until browned.
Add tomato and cook for another 1-2 min. Add the All-Purpose Flour (1 teaspoon) and cook for 2 more minutes while stirring. Add 1/4 cup of water, a pinch of Kosher Salt (to taste) and Ground Black Pepper (to taste) and bring to a boil. Turn down heat and simmer for 8-10 min.
While the mushroom are cooking, drain the potatoes in a colander and put them back in the pot they cooked in. Add Rosemary Sea Salt (1 teaspoon), remaining Unsalted Butter (0.5 ounce) and smash with a potato masher or kitchen spoon until fully incorporated.
When the mushrooms have cooked, remove from heat, and season to taste with Kosher Salt (to taste) and Ground Black Pepper (to taste). Add italian parsley. Divide the potatoes onto two plates, top with the fricasse of mushrooms. Serve and enjoy!