Wash and hull all the fresh strawberries. Set aside about 1 cup of the nicest, firmest strawberries for slicing later. Roughly chop the remaining strawberries (about 1.5 lbs).

In a small saucepan, combine the roughly chopped strawberries, 1/2 cup granulated sugar, and 1/4 cup water. Bring to a simmer over medium heat, stirring occasionally, until the strawberries soften and release their juices, about 5-7 minutes. Remove from heat and let cool slightly.

Carefully transfer the cooled strawberry mixture to a blender or food processor and blend until smooth. Pass the puree through a fine-mesh sieve into a shallow dish to remove any seeds or pulp. Set aside to cool completely. Slice the reserved 1 cup of fresh strawberries.

In a large heatproof bowl, whisk together the egg yolks and 1/2 cup granulated sugar until pale yellow and slightly thickened. Place the bowl over a saucepan of simmering water (creating a double boiler), ensuring the bottom of the bowl does not touch the water. Continue whisking constantly for 5-7 minutes, until the mixture is warm to the touch (around 160°F / 71°C) and forms thick ribbons when the whisk is lifted. Remove from heat and stir in the vanilla extract.

Let the egg yolk mixture cool for a few minutes. Gently fold in the room temperature mascarpone cheese until just combined and smooth. In a separate cold bowl, using an electric mixer, beat the cold heavy cream until soft peaks form. Gently fold the whipped cream into the mascarpone mixture in two additions until no streaks remain, being careful not to overmix.

Quickly dip each ladyfinger into the cooled strawberry puree, turning once to lightly coat but not saturate. Arrange a single layer of dipped ladyfingers in the bottom of an 8x8 inch baking dish (or a similar 2-quart capacity dish). You might need to break some ladyfingers to fit snugly.

Spread half of the mascarpone cream evenly over the ladyfingers. Arrange half of the sliced fresh strawberries in a single layer over the cream. Repeat with another layer of dipped ladyfingers, the remaining mascarpone cream, and the remaining sliced fresh strawberries.

Cover the dish tightly with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, to allow the flavors to meld and the tiramisu to set beautifully. Before serving, dust generously with powdered sugar and garnish with a few extra fresh strawberry slices if desired.