Preheat oven to 375˚F. Transfer the crust to a 10-inch tart pan and gently press into the pan and up the sides. Trim the edges using a butter knife. Bake until the pie crust turns golden brown, 20 to 25 minutes. If the crust bubbles up in any spot, gently flatten them out as soon as the crust comes out of the oven. Let cool for at least 20 minutes before filling. 

In a heavy-bottomed saucepan over medium heat, whisk together the half-and-half, egg, egg yolks, 3 tablespoons sugar, and kosher salt. Cook, whisking often, until the eggs have cooked and the mixture comes to a boil and curdles, 6 to 7 minutes. Transfer to a blender along with the chocolate chips and malted milk powder, scraping down any residual mixture stuck to the pot. Cover the lid with a kitchen towel and blend until smooth, 30 to 45 seconds. Let the mixture cool for about 15 minutes, then carefully pour the mixture into the cooked shell. Refrigerate the tart for about 4 hours or up to overnight to set. 

Prepare a parchment paper-lined baking sheet. In a medium pan over medium-high heat, cook 3 tablespoons water with the remaining ¼ cup sugar until it begins to turn a dark amber color, 4 to 5 minutes. Immediately remove the pan from the heat, and stir in the pretzels to coat thoroughly. Spread out onto the prepared baking sheet and let cool. 

When the filling is set, sprinkle the pretzel mixture on top and serve.