1. Preheat oven to 350degreesF. Spray 2 baking sheets with vegetable cooking spray, or line with parchment paper.
2. In a small bowl, sour milk by combining the milk and vinegar. Set aside.
3. In a large bowl, use an electric mixer on medium speed to cream shortening and brown sugar until light and fluffy, about 2 to 3 minutes. Mix in eggs until well incorporated, about 1 minute. Mix in reserved sour milk and vanilla.
4. In a separate bowl, sift together flour, salt, baking soda, and cinnamon. Add gradually to the creamed mixture and mix until thoroughly incorporated. The dough should be smooth, thick, and moist, like a thick cake batter.
5. Drop dough by the tablespoonful onto the prepared baking sheets, about 1 1/2 to 2 inches apart (cookies will spread). Flatten each cookie slightly and make a slight well in the center. Place 1 tsp. jam in the well, then top with an additional 1 tsp. dough. Place one pan of cookies in the oven while you prepare cookies on the second pan.
6. Bake at 350degreesF for 10 to 12 minutes. The cookies will spread and turn pale gold. Let rest on baking sheet for 1 minute, then transfer to a rack to cool. Serve at room temperature. Store in an airtight container, with waxed paper between layers.
Source: fresh magazine May, June 2010