The trick to gooey, butter, smooth, creamy butter tarts is preventing the formation of sugar crystals.
This is done by using corn syrup, or adding an acid like vinegar or lemon juice to the filling.
Speaking of vinegar, another way to keep the crust from being chewy is to add a bit of vinegar to the dough to help prevent the formation of gluten.
“Canadian” butter tarts use around 1/3 maple syrup
Raisins (dried currants?) and nuts are optional, use around 1/2 cup total.
Crust
2 1/4 cup flour (280 g)
2 tsp sugar (10 ml)
1 tsp salt (5 ml)
2/3 cup unsalted butter (155 g), very cold, cut into small cubes
1/3 cup (85 ml) very cold water
Filling
1/3 cup (80 g) unsalted, melted butter
1 cup (200 g) packed (light) brown sugar (or regular sugar + molasses 1/2 tbsp for light, 1 tbsp for regular)
2 tbsp (30 ml) heavy whipping cream
1 tsp (5 ml) vanilla extract
1/4 (1.25 ml) salt
1 (1) large egg
Make the dough like my pie recipe
Chill 30-60 mins, roll 1/4″ thick cut into 4″ circles, place into regular (2″ diameter at bottom) 12 cupcake tray
put pan in fridge
Preheat oven to 400F
Blind bake 20 mins, bottom rack with silicone cup liners filled with pie weights/beans.
Let cool before removing molds.
Reduce oven to 375F
Cream butter & sugar, add other ingredients. put some optional fun stuff in the bottom of each tart cup, divide filling evenly, bake until set and edges are golden brown.
Middle rack 15 minutes for gooey filling, 20 for firm.
Remove from oven, let cool 5 mins until firm, gently twist to remove from muffin tin.