Step 1: In a large bowl, whisk together 1 ½ cups all-purpose flour, ½ cup granulated sugar, and ¼ teaspoon salt.
Step 2: Add ½ cup (1 stick) very cold, cubed unsalted butter to the flour mixture. Using your fingertips, a pastry blender, or a food processor, cut the butter into the flour until the mixture resembles coarse meal with some pea-sized pieces of butter remaining.
Step 3: Gradually add ¼ cup ice water, one tablespoon at a time, mixing until the dough just comes together. Be careful not to overmix.
Step 4: Form the dough into a disc, wrap it tightly in plastic wrap, and refrigerate for at least 30 minutes (or up to 2 days).
Step 5: On a lightly floured surface, roll out the chilled dough into a 12-inch circle. Carefully transfer the dough to a 9-inch tart pan with a removable bottom. Press the dough gently into the bottom and up the sides of the pan. Trim any excess dough.
Step 6: Prick the bottom of the tart shell all over with a fork. Place the tart pan in the freezer for 15 minutes.
Step 7: Preheat your oven to 375°F (190°C). Line the chilled tart shell with parchment paper or foil and fill with pie weights or dried beans.
Step 8: Bake for 15 minutes, then carefully remove the parchment and weights. Continue to bake for another 10-15 minutes, or until the crust is lightly golden brown. Let cool completely on a wire rack.
Step 9: In a heavy-bottomed saucepan, combine 1 cup granulated sugar and ¼ cup water. Cook over medium heat, stirring gently until the sugar dissolves. Once dissolved, stop stirring.
Step 10: Continue to cook, swirling the pan occasionally, until the sugar syrup turns a deep amber color (about 8-12 minutes). Watch carefully, as it can burn quickly.
Step 11: Immediately and carefully, pour ½ cup warmed heavy cream into the caramel. Whisk continuously until smooth.
Step 12: Remove from heat and whisk in ¼ cup (½ stick) room temperature unsalted butter, ¼ cup smoked maple syrup, 2 tablespoons white miso paste, and 1 teaspoon vanilla extract until fully incorporated and smooth.
Step 13: Stir in ½ teaspoon flaky sea salt. Taste and adjust if necessary.
Step 14: Pour the warm Smoked Maple Miso Caramel filling into the cooled tart shell. Gently tap the tart on the counter a few times to release any air bubbles.
Step 15: Refrigerate for at least 3-4 hours, or until the caramel is completely set. For best results, chill overnight.
Step 16 (Optional Ganache): Place 4 ounces finely chopped dark chocolate in a heatproof bowl. Heat ½ cup heavy cream in a small saucepan over medium heat until it just begins to simmer. Pour hot cream over chocolate, let sit 5 minutes, then whisk until smooth and glossy.
Step 17 (Optional Ganache): Pour the ganache over the set Smoked Maple Miso Caramel Tart, spreading it evenly. Refrigerate until ganache is set, about 30 minutes to an hour. Garnish with additional flaky sea salt before serving, if desired.