Method:

• Make the crust: In a food processor fitted with a metal blade, add the flour, salt, and sugar. 
• Pulse briefly to combine. Add the cold butter and process until you have pea-size clumps of butter, about 8 seconds.
• Sprinkle the cold water over the mixture and process until moistened and clumpy, about 8 seconds. 
• Transfer the dough to a lightly floured surface and knead a few times until it comes together into a homogeneous ball. 
• Pat and knead the dough into a 6-inch disk, adding flour and turning the dough as necessary so it doesn’t stick. Wrap the dough in plastic wrap and refrigerate for at least 30 minutes or up to 3 days. 

Make the meringue:

• Preheat oven to 225°F.
• Place the salt, egg whites, and cream of tartar in a stand mixer with a whisk attachment. 
• Whisk until soft peaks form, then add the sugar gradually until it doubles in volume and the mix is glossy. 
• Fold in the wholegrain mustard and 1 tsp of vanilla powder, then place in a piping bag with a small round piping tip.
• Pipe 3-inch-long sticks into a tray lined with parchment and bake in the oven for an hour or until baked and crunchy. 
• Let it cool and set aside.
• Preheat the oven to 375°F and set an oven rack in the middle position.
• Take the dough from the fridge and unwrap onto a lightly floured surface (if it’s been in the refrigerator for over 30 minutes, you may need to knead it until it’s malleable enough to roll). 
• Roll the dough to about ⅛ inch thick, adding flour and turning as necessary so it doesn’t stick. Don’t worry about the shape.
• Using a 4-inch-diameter cookie or biscuit cutter, cut the dough into as many circles as possible. Line each cup of an ungreased 12-cup muffin pan with dough circles, gently nudging it down into the bottom creases of the pan. 
• The top edge of the dough circle should come up to the top of the cup. Gather the scraps and reroll the dough if you need additional circles. Chill the pan with dough in the freezer while you prepare the filling.
• Make the filling: In a medium bowl, whisk together the Maille Honey Dijon, brown sugar, maple syrup, butter, egg, vinegar, vanilla, and salt.
• Divide the pecans and raisins (if using) among the pastry-lined muffin cups, then pour the filling evenly into the muffin cups. 
• Bake for about 25 minutes, until the tarts are golden brown, bubbling, and set. 

Make the Chantilly:

• Place the maple syrup and heavy cream in a medium stainless-steel bowl and whip until firm. 
• Place in a piping bag with a small Saint Honoré tip.
• Set aside in the fridge. 
• Once butter tarts are cooked, let them cool on a wire rack for a few minutes, then run a butter knife around the edge of each tart to loosen. 
• Let the tarts cool completely in the pan, then remove. 
• Pipe the Chantilly on each tart, garnish with wholegrain mustard meringues and mint flowers (optional).

Serve at room temperature. Bon appétit!