For crust, combine flour, sugar, and salt in the bowl of a food processor. Sprinkle over butter cubes and pulse until butter breaks up into pea-sized chunks. Add egg and pulse until just incorporated. Dump mixture out onto a clean surface and knead a few times to bring it together in a ball. Don't overwork it, especially if your kitchen is on the warm side: we want to keep the dough as cold as possible so the butter never fully melts until it is baked.

If you are making 6-inch tarts, split the dough in two and form into a disc shape. Wrap tightly in plastic wrap and refrigerate at least 30 minutes or overnight. If you are only making one tart today, you can freeze the second dough disc for later (you can also shape it in the tart shell and freeze it then too).

To make matcha pastry cream, heat milk in a small saucepan set over medium-low heat until it just begins to bubble and steam (do not let it scald). While milk is heating, whisk together sugar, flour, cornstarch, matcha and salt in a bowl. Add egg yolks (save the whites for the meringues) and whisk until mixture forms a smooth paste. If you need to, spoon a tablespoon or so of milk from the saucepan into the yolk mixture to help it come together smoothly.

Gradually ladle a little of the hot milk mixture, about 1/4 cup at a time, into the matcha mixture, whisking constantly, until about half of the milk has been incorporated and mixture is warm to the touch. This will 'temper' the egg yolks rather than cook them. Pour mixture back into saucepan with the rest of the milk, whisking to incorporate.

Return saucepan to low heat (emphasis on LOW here - if you rush this, you'll end up with chunky pastry cream which is less than ideal). Continue to stir, alternating between a whisk and a rubber spatula to scrape the sides and the bottom of the pan. Continue to gently heat, stirring regularly, until pastry cream has thickened to the consistency of pudding and starts to bubble in the center.

Remove from heat and add butter, whisking gently until completely melted and smooth. If you notice any chunks at all in your pastry cream, press it through a fine mesh sieve to remove any bits of cooked egg.

Transfer to a bowl, then press a layer of plastic wrap onto the surface of the pastry cream to prevent a skin from forming. Refrigerate at least 2 hours or until completely cool.

To make meringues, preheat oven to 225 degrees F, and arrange baking racks to sit in the bottom 1/3 and top 1/3 of the oven.

Beat reserved egg whites in a stand mixer fitted with the whisk attachment until doubled in volume. With the mixer running, gradually pour in sugar, and continue to whip on medium-high speed until mixture is stiff and fluffy, about 5 to 7 minutes more. Sift about a third of the powdered sugar over top of bowl and fold until incorporated. Repeat with remaining powdered sugar in two additions until incorporated.

Fit a large piping bag with a small star tip (I used Wilton #21) and fill with half of meringue mixture. Line two baking sheets with parchment or silicone baking mats. Pipe small kisses of varying sizes into rows on baking sheets. They won't spread in the oven, so you can pipe them pretty close together. Refill your pastry bag and repeat on second baking sheet. If desired, spoon a bit of matcha powder into a small sieve and dust tops of meringues.

Bake for 20 to 30 minutes or until meringues easily release from the baking sheets, but the centers are still soft. Turn off oven, prop the door open with a wooden spoon, and let the meringues cool with the oven.

To bake your tart shells, you can either use a tart pan with a removable bottom, or a French tart ring set on a parchment-lined baking sheet. Dust a surface liberally with flour and unwrap one dough disc. Start by pounding the dough with a heavy rolling pin to soften it slightly, rotating the rolling pin at different angles to it flattens evenly. Then roll out into approximately 9-inch round. If the dough gets too soft at any point, pop it back in the fridge to firm it back up (it helps to roll out on a piece of parchment to make this easier). Gently drape the rolled dough into the tart shell, easing the edges into the corners and taking are not to stretch the dough. If you are using a straight sided tart ring, you can also opt to shape the dough in two pieces, by cutting out a round for the bottom, then rolling out a long piece of dough for the sides. Cut into an even strip using a ruler, then lay vertically onto the base, pressing lightly to adhere. Trim edges flush with the top edge. Place in the freezer for for 15 to 30 minutes or until completely firm.

Preheat oven to 375 degrees F (don't forget to take your meringues out if they are still in there!) Line frozen tart shell with parchment (I find it helps to crumple the parchment so it'll go into the corners more easily. Fill with sugar, pressing into the corners as best you can.

Bake for 12 to 15 minutes or until crust is starting to brown. Gently lift out parchment with sugar, then return shell to oven for an additional 3 to 5 minutes or until golden brown. Let cool completely.

To assemble, whisk the chilled pastry cream a few times to smooth it out, then spread into the cooled tart shell. Top with a ring of sliced strawberries, and, if desired, decorate with mini meringue kisses and mint leaves. If not serving right away, keep refrigerated, though I recommend at placing the berries and meringues as close to serving time as possible.