Place your butter & chocolate chips into a double boiler & allow to melt completely over the steaming water. Stir frequently. WHILE the chocolate butter is melting. Place the eggs & sugar into the bowl of your mixer. With the whisk attachment mix on medium-high speed until they become light & thick (about 8-9 mins). When light & thick add the flour & mix together. SLOWLY & GRADUALLY pour the chocolate/butter mixture into the egg mixture. Mixing on low until well combined & develops a glossy sheen (about 5-6 mins).
Preheat your oven to 350 degrees. WHILE the mixture is finishing it’s final mixing (turning glossy) GENEROUSLY spray 4 small ramekins with cooking spray. When the batter is finished it’s time to assemble:.
Place your sprayed ramekins onto a cooking tray. Ladle batter HALFWAY up the side of each ramekin. Then, spoon 1 tbsp of Nutella into each ramekin. Finish ladling remainder of batter into each ramekin (do not overfill). Bake ramekins for 10-14 mins until outside is solid and top appears to be soft (but NOT jiggly).
WHILE cakes are cooking, chop your walnuts & cut your strawberries. When cakes are ready CAREFULLY remove them from oven, place a plate on top of each one and quickly invert it. With a kitchen towel remove the ramekin, cake should fall right out. Garnish with nuts & strawberries. Serve immediately!