Line an 8x8 or 9x9 inch pan with parchment paper, leaving an overhang, and lightly grease. Measure all ingredients for both fudge and swirl components.

Rinse and hull fresh strawberries (no need to thaw frozen). Puree strawberries until smooth. Pour puree into a small saucepan with 2 tbsp sugar and optional ½ tsp lemon juice. Simmer over medium-low heat, stirring frequently, until thickened to a jam-like consistency (10-20 minutes). Set aside to cool.

In a heavy-bottomed saucepan, combine 3 cups granulated sugar, ¾ cup butter pieces, and ⅔ cup evaporated milk. Cook over medium heat, stirring until butter melts and sugar dissolves. Bring to a steady rolling boil.

Attach a candy thermometer and continue boiling, stirring occasionally, until the mixture reaches 234-238°F (112-114°C) (soft ball stage), about 5-8 minutes.

Immediately remove from heat. Stir in 1 jar marshmallow crème, 12 oz white chocolate (chopped/chips), 1 tsp vanilla extract, and ¼ tsp salt. Stir vigorously until all ingredients are melted, smooth, and glossy.

Pour about three-quarters of the hot fudge base into the prepared pan. Randomly dollop spoonfuls of the cooled strawberry reduction over the fudge. Optionally, spoon remaining white fudge over the strawberry dollops. Gently drag a knife or skewer through the fudge in a swirling motion to marble the colors without fully mixing.

Allow the fudge to cool completely at room temperature (1-2 hours), then transfer to the refrigerator to chill and firm up for at least 2-4 hours, or ideally overnight.

Once firm, use the parchment paper to lift the fudge from the pan onto a cutting board. Trim edges and slice into 1-inch or 1½-inch squares. Wipe the knife between cuts for clean edges. Store in an airtight container at room temperature for up to a week, or in the refrigerator for up to two weeks. Can be frozen for up to 3 months.