Dice the onion finely and mince the garlic cloves—this ensures even cooking and proper flavor distribution. Slice the mushrooms into even pieces, about quarter-inch thick. Have all ingredients measured and ready before you start cooking. Heat the olive oil in a large, heavy-bottomed pan or Dutch oven over medium heat until it shimmers, then add the diced onion and minced garlic. Cook for 4-5 minutes, stirring occasionally, until the onion becomes translucent and fragrant—this develops a sweet, aromatic base that will carry all the flavors of the dish.

Add the sliced mushrooms to the pan with the aromatic base and cook for 2-3 minutes over medium-high heat, stirring frequently. The mushrooms will release their moisture and begin to caramelize slightly—this concentrates their earthy, umami flavors that form the backbone of this stroganoff. I like to let them cook undisturbed for the first minute to develop a light golden color on the cut sides, which adds depth to the final sauce.

Stir in the tomato paste and cook for 1 minute, allowing it to caramelize slightly in the hot pan—this removes any raw flavor and deepens the sauce. Pour in the beef broth, then add the Dijon mustard, smoked paprika, Italian herbs, and bay leaf. Stir well to combine, then reduce heat to low and simmer gently for 10 minutes. This simmering time allows the flavors to marry together and the sauce to thicken slightly. I find that the paprika and mustard need this time to fully integrate and lose any harsh edges.

Remove the pan from heat and stir in the creme fraiche until fully incorporated—taking it off heat prevents the dairy from curdling or separating. Add the roast beef strips, then return the pan to low heat and simmer gently for 5 minutes, stirring occasionally, until the beef is warmed through and coated in the creamy sauce. The residual heat should gently warm the beef without toughening it, keeping it tender and succulent. Remove the bay leaf, taste for seasoning, and adjust salt and pepper as needed.

Transfer the stroganoff to a serving dish or individual bowls. Garnish generously with freshly chopped parsley, which adds a bright, fresh contrast to the rich, savory sauce.