Lightly butter or spray an 8x8-inch (20x20 cm) square pan. Line it with parchment paper, leaving some overhang on two sides to create handles. Smooth out any large wrinkles so the fudge will have neat edges.

In a large microwave-safe bowl, combine the white chocolate chips, sweetened condensed milk, and butter. Microwave on 50% power for 45–60 seconds, then stir very well. Continue microwaving in 20–30 second bursts at 50% power, stirring between each burst, until the mixture is smooth and glossy. Do not let it boil; it should be warm and fully melted. Residual heat will finish melting any small bits as you stir.

Alternatively, add the white chocolate chips, sweetened condensed milk, and butter to a medium heavy-bottomed saucepan. Warm over low heat, stirring constantly, until the white chocolate is fully melted and the mixture is smooth. Take your time and avoid high heat to prevent scorching or seizing.

Once the base is melted and smooth, sprinkle the strawberry gelatin mix evenly over the top. Stir steadily until the gelatin is fully dissolved and the mixture turns a deep, even pink. If using crushed freeze-dried strawberries, stir them in now; they will slightly thicken the mixture and boost the natural strawberry aroma.

Stir in the vanilla extract and a pinch of fine sea salt. Taste a tiny bit carefully (it will be warm and sweet). If it tastes too one-note or overly sweet, add a very small extra pinch of salt to balance the flavors.

Immediately pour the strawberry fudge mixture into the prepared pan. Use a small offset spatula or the back of a spoon to spread it evenly into the corners and smooth the surface. Work fairly quickly, as the mixture will begin to thicken as it cools.

While the surface is still warm and soft, add any desired toppings: Valentine’s sprinkles or nonpareils, extra crushed freeze-dried strawberries, or a decorative white chocolate drizzle. Press sprinkles or berry pieces very gently so they adhere without sinking.

Place the pan in the refrigerator and chill for at least 2 hours, or until the fudge is firm enough to slice cleanly. For the cleanest cuts, chill 3–4 hours. For a slightly firmer, chewier texture, chill overnight.

Use the parchment handles to lift the block of fudge from the pan and transfer it to a cutting board. With a long, sharp knife, cut into 1-inch squares or rectangles, wiping the blade with a warm, damp cloth between cuts for neat edges. Serve at cool room temperature.