1. Line muffin tray with cupcake liners. Also, line cookie sheet or baking tray with parchment/baking paper. In bowl of stand mixer, add peanut butter and butter. Beat together until smooth. Sift in powdered sugar and salt, beat until soft & thick dough forms.
2. Scoop 1tbs-balls of peanut butter mixture onto prepared tray. Lightly press balls with finger tips to shape into patties. Place tray in fridge for at least 15 minutes.
3. While peanut butter patties chill, melt chocolate. Place small saucepan with 2 inches water in bottom on medium heat. Place chocolate in small heatproof bowl and place bowl on top of saucepan, ensuring bottom of bowl will not touch water below. Gently stir chocolate until melted and completely smooth..
4. Once chocolate has melted, remove saucepan from heat but keep bowl on top. Spoon 1⁄2-1tbs melted chocolate into each muffin cup. Tap tray on counter to make sure chocolate layer is even. Place muffin tin in fridge for 5-10 minutes to slightly firm up chocolate.
5. Once chocolate in muffin cups has begun to set, remove muffin tray and peanut butter patties on baking sheet from fridge. Place one peanut butter patty in each muffin cup, on top of chocolate. Make sure there is space between peanut butter patty and side-wall of muffin liner.
6. Scoop 1tsp strawberry preserves onto each patty in muffin cups. Gently smooth/spread jam into semi-even layer on top of patties with back of spoon.
7. Using remaining chocolate from double boiler (reheating if necessary), scoop 1.5-2tbs chocolate into each muffin cup, shaking muffin pan to make sure chocolate settles around each patty/jam insert.
8. Place tray in fridge until fully set, at least 60 minutes.